Reemplazo de caracteres acentuados php

Estoy tratando de reemplazar los caracteres acentuados con los reemplazos normales. A continuación se muestra lo que estoy haciendo actualmente.

    $string = "Éric Cantona";
    $strict = strtolower($string);

    echo "After Lower: ".$strict;

    $patterns[0] = '/[á|â|à|å|ä]/';
    $patterns[1] = '/[ð|é|ê|è|ë]/';
    $patterns[2] = '/[í|î|ì|ï]/';
    $patterns[3] = '/[ó|ô|ò|ø|õ|ö]/';
    $patterns[4] = '/[ú|û|ù|ü]/';
    $patterns[5] = '/æ/';
    $patterns[6] = '/ç/';
    $patterns[7] = '/ß/';
    $replacements[0] = 'a';
    $replacements[1] = 'e';
    $replacements[2] = 'i';
    $replacements[3] = 'o';
    $replacements[4] = 'u';
    $replacements[5] = 'ae';
    $replacements[6] = 'c';
    $replacements[7] = 'ss';

    $strict = preg_replace($patterns, $replacements, $strict);
    echo "Final: ".$strict;

Esto me da:

    After Lower: éric cantona
    Final: ric cantona

Lo anterior me da ric cantonaque quiero que la salida sea eric cantona.

¿Alguien puede ayudarme con lo que estoy haciendo mal?

He intentado todo tipo según las variaciones enumeradas en las respuestas, pero lo siguiente funcionó:

$unwanted_array = array(    'Š'=>'S', 'š'=>'s', 'Ž'=>'Z', 'ž'=>'z', 'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E',
                            'Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U',
                            'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss', 'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c',
                            'è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o',
                            'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'þ'=>'b', 'ÿ'=>'y' );
$str = strtr( $str, $unwanted_array );

Para eliminar los signos diacríticos, use iconv:

$val = iconv('ISO-8859-1','ASCII//TRANSLIT',$val);

o

$val = iconv('UTF-8','ASCII//TRANSLIT',$val);

tenga en cuenta que php tiene un error extraño en el sentido de que (¿a veces?) Necesita tener una configuración regional para que estas conversiones funcionen, usando setlocale ().

edición probada, saca todos los signos diacríticos de la caja:

$val = "á|â|à|å|ä ð|é|ê|è|ë í|î|ì|ï ó|ô|ò|ø|õ|ö ú|û|ù|ü æ ç ß abc ABC 123";
echo iconv('UTF-8','ASCII//TRANSLIT',$val); 

salida (actualizado 2019-12-30)

a|a|a|a|a d|e|e|e|e i|i|i|i o|o|o|o|o|o u|u|u|u ae c ss abc ABC 123

Tenga en cuenta que ðestá correctamente transcrito en en dlugar de o, como en la respuesta aceptada.

Acabo de encontrar la respuesta de Lizard que es extremadamente útil, especialmente cuando haces una clasificación. No es hermoso cuántos caracteres necesitamos para decir casi lo mismo;)

Si alguien más está buscando una solución integral (según los comentarios anteriores), aquí está la copia y pegado:

/**
 * Replace language-specific characters by ASCII-equivalents.
 * @param string $s
 * @return string
 */
public static function normalizeChars($s) {
    $replace = array(
        'ъ'=>'-', 'Ь'=>'-', 'Ъ'=>'-', 'ь'=>'-',
        'Ă'=>'A', 'Ą'=>'A', 'À'=>'A', 'Ã'=>'A', 'Á'=>'A', 'Æ'=>'A', 'Â'=>'A', 'Å'=>'A', 'Ä'=>'Ae',
        'Þ'=>'B',
        'Ć'=>'C', 'ץ'=>'C', 'Ç'=>'C',
        'È'=>'E', 'Ę'=>'E', 'É'=>'E', 'Ë'=>'E', 'Ê'=>'E',
        'Ğ'=>'G',
        'İ'=>'I', 'Ï'=>'I', 'Î'=>'I', 'Í'=>'I', 'Ì'=>'I',
        'Ł'=>'L',
        'Ñ'=>'N', 'Ń'=>'N',
        'Ø'=>'O', 'Ó'=>'O', 'Ò'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'Oe',
        'Ş'=>'S', 'Ś'=>'S', 'Ș'=>'S', 'Š'=>'S',
        'Ț'=>'T',
        'Ù'=>'U', 'Û'=>'U', 'Ú'=>'U', 'Ü'=>'Ue',
        'Ý'=>'Y',
        'Ź'=>'Z', 'Ž'=>'Z', 'Ż'=>'Z',
        'â'=>'a', 'ǎ'=>'a', 'ą'=>'a', 'á'=>'a', 'ă'=>'a', 'ã'=>'a', 'Ǎ'=>'a', 'а'=>'a', 'А'=>'a', 'å'=>'a', 'à'=>'a', 'א'=>'a', 'Ǻ'=>'a', 'Ā'=>'a', 'ǻ'=>'a', 'ā'=>'a', 'ä'=>'ae', 'æ'=>'ae', 'Ǽ'=>'ae', 'ǽ'=>'ae',
        'б'=>'b', 'ב'=>'b', 'Б'=>'b', 'þ'=>'b',
        'ĉ'=>'c', 'Ĉ'=>'c', 'Ċ'=>'c', 'ć'=>'c', 'ç'=>'c', 'ц'=>'c', 'צ'=>'c', 'ċ'=>'c', 'Ц'=>'c', 'Č'=>'c', 'č'=>'c', 'Ч'=>'ch', 'ч'=>'ch',
        'ד'=>'d', 'ď'=>'d', 'Đ'=>'d', 'Ď'=>'d', 'đ'=>'d', 'д'=>'d', 'Д'=>'D', 'ð'=>'d',
        'є'=>'e', 'ע'=>'e', 'е'=>'e', 'Е'=>'e', 'Ə'=>'e', 'ę'=>'e', 'ĕ'=>'e', 'ē'=>'e', 'Ē'=>'e', 'Ė'=>'e', 'ė'=>'e', 'ě'=>'e', 'Ě'=>'e', 'Є'=>'e', 'Ĕ'=>'e', 'ê'=>'e', 'ə'=>'e', 'è'=>'e', 'ë'=>'e', 'é'=>'e',
        'ф'=>'f', 'ƒ'=>'f', 'Ф'=>'f',
        'ġ'=>'g', 'Ģ'=>'g', 'Ġ'=>'g', 'Ĝ'=>'g', 'Г'=>'g', 'г'=>'g', 'ĝ'=>'g', 'ğ'=>'g', 'ג'=>'g', 'Ґ'=>'g', 'ґ'=>'g', 'ģ'=>'g',
        'ח'=>'h', 'ħ'=>'h', 'Х'=>'h', 'Ħ'=>'h', 'Ĥ'=>'h', 'ĥ'=>'h', 'х'=>'h', 'ה'=>'h',
        'î'=>'i', 'ï'=>'i', 'í'=>'i', 'ì'=>'i', 'į'=>'i', 'ĭ'=>'i', 'ı'=>'i', 'Ĭ'=>'i', 'И'=>'i', 'ĩ'=>'i', 'ǐ'=>'i', 'Ĩ'=>'i', 'Ǐ'=>'i', 'и'=>'i', 'Į'=>'i', 'י'=>'i', 'Ї'=>'i', 'Ī'=>'i', 'І'=>'i', 'ї'=>'i', 'і'=>'i', 'ī'=>'i', 'ij'=>'ij', 'IJ'=>'ij',
        'й'=>'j', 'Й'=>'j', 'Ĵ'=>'j', 'ĵ'=>'j', 'я'=>'ja', 'Я'=>'ja', 'Э'=>'je', 'э'=>'je', 'ё'=>'jo', 'Ё'=>'jo', 'ю'=>'ju', 'Ю'=>'ju',
        'ĸ'=>'k', 'כ'=>'k', 'Ķ'=>'k', 'К'=>'k', 'к'=>'k', 'ķ'=>'k', 'ך'=>'k',
        'Ŀ'=>'l', 'ŀ'=>'l', 'Л'=>'l', 'ł'=>'l', 'ļ'=>'l', 'ĺ'=>'l', 'Ĺ'=>'l', 'Ļ'=>'l', 'л'=>'l', 'Ľ'=>'l', 'ľ'=>'l', 'ל'=>'l',
        'מ'=>'m', 'М'=>'m', 'ם'=>'m', 'м'=>'m',
        'ñ'=>'n', 'н'=>'n', 'Ņ'=>'n', 'ן'=>'n', 'ŋ'=>'n', 'נ'=>'n', 'Н'=>'n', 'ń'=>'n', 'Ŋ'=>'n', 'ņ'=>'n', 'ʼn'=>'n', 'Ň'=>'n', 'ň'=>'n',
        'о'=>'o', 'О'=>'o', 'ő'=>'o', 'õ'=>'o', 'ô'=>'o', 'Ő'=>'o', 'ŏ'=>'o', 'Ŏ'=>'o', 'Ō'=>'o', 'ō'=>'o', 'ø'=>'o', 'ǿ'=>'o', 'ǒ'=>'o', 'ò'=>'o', 'Ǿ'=>'o', 'Ǒ'=>'o', 'ơ'=>'o', 'ó'=>'o', 'Ơ'=>'o', 'œ'=>'oe', 'Œ'=>'oe', 'ö'=>'oe',
        'פ'=>'p', 'ף'=>'p', 'п'=>'p', 'П'=>'p',
        'ק'=>'q',
        'ŕ'=>'r', 'ř'=>'r', 'Ř'=>'r', 'ŗ'=>'r', 'Ŗ'=>'r', 'ר'=>'r', 'Ŕ'=>'r', 'Р'=>'r', 'р'=>'r',
        'ș'=>'s', 'с'=>'s', 'Ŝ'=>'s', 'š'=>'s', 'ś'=>'s', 'ס'=>'s', 'ş'=>'s', 'С'=>'s', 'ŝ'=>'s', 'Щ'=>'sch', 'щ'=>'sch', 'ш'=>'sh', 'Ш'=>'sh', 'ß'=>'ss',
        'т'=>'t', 'ט'=>'t', 'ŧ'=>'t', 'ת'=>'t', 'ť'=>'t', 'ţ'=>'t', 'Ţ'=>'t', 'Т'=>'t', 'ț'=>'t', 'Ŧ'=>'t', 'Ť'=>'t', '™'=>'tm',
        'ū'=>'u', 'у'=>'u', 'Ũ'=>'u', 'ũ'=>'u', 'Ư'=>'u', 'ư'=>'u', 'Ū'=>'u', 'Ǔ'=>'u', 'ų'=>'u', 'Ų'=>'u', 'ŭ'=>'u', 'Ŭ'=>'u', 'Ů'=>'u', 'ů'=>'u', 'ű'=>'u', 'Ű'=>'u', 'Ǖ'=>'u', 'ǔ'=>'u', 'Ǜ'=>'u', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'У'=>'u', 'ǚ'=>'u', 'ǜ'=>'u', 'Ǚ'=>'u', 'Ǘ'=>'u', 'ǖ'=>'u', 'ǘ'=>'u', 'ü'=>'ue',
        'в'=>'v', 'ו'=>'v', 'В'=>'v',
        'ש'=>'w', 'ŵ'=>'w', 'Ŵ'=>'w',
        'ы'=>'y', 'ŷ'=>'y', 'ý'=>'y', 'ÿ'=>'y', 'Ÿ'=>'y', 'Ŷ'=>'y',
        'Ы'=>'y', 'ž'=>'z', 'З'=>'z', 'з'=>'z', 'ź'=>'z', 'ז'=>'z', 'ż'=>'z', 'ſ'=>'z', 'Ж'=>'zh', 'ж'=>'zh'
    );
    return strtr($s, $replace);
}

Tenga en cuenta algunos cambios leves con respecto a las diéresis alemanas (ä => ae)

Editar: Incluyó más caracteres basados ​​en la publicación de user3682119 (excepto por el símbolo de derechos de autor) y el comentario de daker.

En PHP 5.4, la intlextensión proporciona una nueva clase llamada Transliterator.

Creo que esa es la mejor manera de eliminar los signos diacríticos por dos razones:

1. Transliterator se basa en ICU, por lo que está utilizando las tablas de la biblioteca de ICU. ICU es un gran proyecto, desarrollado durante el año para proporcionar tablas y funcionalidades integrales. Cualquiera que sea la tabla que desee escribir usted mismo, nunca será tan completa como la de ICU.

2. En UTF-8, los personajes se pueden representar de manera diferente. Por ejemplo, el carácter ñ podría guardarse como un carácter único (de varios bytes) o como una combinación de caracteres.˜ (multibyte) (multibyte) y n. Además de esto, algunos caracteres en Unicode son homógrafos: se ven iguales pero tienen diferentes puntos de código. Por esta razón también es importante normalizar la cadena.

Aquí hay un código de muestra, tomado de una vieja respuesta mía :

<?php
$transliterator = Transliterator::createFromRules(':: NFD; :: [:Nonspacing Mark:] Remove; :: NFC;', Transliterator::FORWARD);
$test = ['abcd', 'èe', '€', 'àòùìéëü', 'àòùìéëü', 'tiësto'];
foreach($test as $e) {
    $normalized = $transliterator->transliterate($e);
    echo $e. ' --> '.$normalized."\n";
}
?>

Resultado:

abcd --> abcd
èe --> ee
€ --> €
àòùìéëü --> aouieeu
àòùìéëü --> aouieeu
tiësto --> tiesto

El primer argumento de la clase Transliterator realiza la eliminación de signos diacríticos, así como la normalización de la cadena.

Así que encontré esto en la página php.net para la función preg_replace

// replace accented chars

$string = "Zacarías Ferreíra"; // my definition for string variable
$accents = '/&([A-Za-z]{1,2})(grave|acute|circ|cedil|uml|lig);/';

$string_encoded = htmlentities($string,ENT_NOQUOTES,'UTF-8');

$string = preg_replace($accents,'$1',$string_encoded);

Si tiene problemas de codificación, puede obtener algo como este "ZacarÃÂas FerreÃÂra", simplemente decodifique la cadena y use dicho código de arriba.

$string = utf8_decode("Zacarías Ferreíra");

Esto funcionó para mí:

<?php
setlocale(LC_ALL, "en_US.utf8"); 
$val = iconv('UTF-8','ASCII//TRANSLIT',$val);
?>

Una respuesta actualizada basada en @BurninLeo respuesta 's

function replace_spec_char($subject) {
    $char_map = array(
        "ъ" => "-", "ь" => "-", "Ъ" => "-", "Ь" => "-",
        "А" => "A", "Ă" => "A", "Ǎ" => "A", "Ą" => "A", "À" => "A", "Ã" => "A", "Á" => "A", "Æ" => "A", "Â" => "A", "Å" => "A", "Ǻ" => "A", "Ā" => "A", "א" => "A",
        "Б" => "B", "ב" => "B", "Þ" => "B",
        "Ĉ" => "C", "Ć" => "C", "Ç" => "C", "Ц" => "C", "צ" => "C", "Ċ" => "C", "Č" => "C", "©" => "C", "ץ" => "C",
        "Д" => "D", "Ď" => "D", "Đ" => "D", "ד" => "D", "Ð" => "D",
        "È" => "E", "Ę" => "E", "É" => "E", "Ë" => "E", "Ê" => "E", "Е" => "E", "Ē" => "E", "Ė" => "E", "Ě" => "E", "Ĕ" => "E", "Є" => "E", "Ə" => "E", "ע" => "E",
        "Ф" => "F", "Ƒ" => "F",
        "Ğ" => "G", "Ġ" => "G", "Ģ" => "G", "Ĝ" => "G", "Г" => "G", "ג" => "G", "Ґ" => "G",
        "ח" => "H", "Ħ" => "H", "Х" => "H", "Ĥ" => "H", "ה" => "H",
        "I" => "I", "Ï" => "I", "Î" => "I", "Í" => "I", "Ì" => "I", "Į" => "I", "Ĭ" => "I", "I" => "I", "И" => "I", "Ĩ" => "I", "Ǐ" => "I", "י" => "I", "Ї" => "I", "Ī" => "I", "І" => "I",
        "Й" => "J", "Ĵ" => "J",
        "ĸ" => "K", "כ" => "K", "Ķ" => "K", "К" => "K", "ך" => "K",
        "Ł" => "L", "Ŀ" => "L", "Л" => "L", "Ļ" => "L", "Ĺ" => "L", "Ľ" => "L", "ל" => "L",
        "מ" => "M", "М" => "M", "ם" => "M",
        "Ñ" => "N", "Ń" => "N", "Н" => "N", "Ņ" => "N", "ן" => "N", "Ŋ" => "N", "נ" => "N", "ʼn" => "N", "Ň" => "N",
        "Ø" => "O", "Ó" => "O", "Ò" => "O", "Ô" => "O", "Õ" => "O", "О" => "O", "Ő" => "O", "Ŏ" => "O", "Ō" => "O", "Ǿ" => "O", "Ǒ" => "O", "Ơ" => "O",
        "פ" => "P", "ף" => "P", "П" => "P",
        "ק" => "Q",
        "Ŕ" => "R", "Ř" => "R", "Ŗ" => "R", "ר" => "R", "Р" => "R", "®" => "R",
        "Ş" => "S", "Ś" => "S", "Ș" => "S", "Š" => "S", "С" => "S", "Ŝ" => "S", "ס" => "S",
        "Т" => "T", "Ț" => "T", "ט" => "T", "Ŧ" => "T", "ת" => "T", "Ť" => "T", "Ţ" => "T",
        "Ù" => "U", "Û" => "U", "Ú" => "U", "Ū" => "U", "У" => "U", "Ũ" => "U", "Ư" => "U", "Ǔ" => "U", "Ų" => "U", "Ŭ" => "U", "Ů" => "U", "Ű" => "U", "Ǖ" => "U", "Ǜ" => "U", "Ǚ" => "U", "Ǘ" => "U",
        "В" => "V", "ו" => "V",
        "Ý" => "Y", "Ы" => "Y", "Ŷ" => "Y", "Ÿ" => "Y",
        "Ź" => "Z", "Ž" => "Z", "Ż" => "Z", "З" => "Z", "ז" => "Z",
        "а" => "a", "ă" => "a", "ǎ" => "a", "ą" => "a", "à" => "a", "ã" => "a", "á" => "a", "æ" => "a", "â" => "a", "å" => "a", "ǻ" => "a", "ā" => "a", "א" => "a",
        "б" => "b", "ב" => "b", "þ" => "b",
        "ĉ" => "c", "ć" => "c", "ç" => "c", "ц" => "c", "צ" => "c", "ċ" => "c", "č" => "c", "©" => "c", "ץ" => "c",
        "Ч" => "ch", "ч" => "ch",
        "д" => "d", "ď" => "d", "đ" => "d", "ד" => "d", "ð" => "d",
        "è" => "e", "ę" => "e", "é" => "e", "ë" => "e", "ê" => "e", "е" => "e", "ē" => "e", "ė" => "e", "ě" => "e", "ĕ" => "e", "є" => "e", "ə" => "e", "ע" => "e",
        "ф" => "f", "ƒ" => "f",
        "ğ" => "g", "ġ" => "g", "ģ" => "g", "ĝ" => "g", "г" => "g", "ג" => "g", "ґ" => "g",
        "ח" => "h", "ħ" => "h", "х" => "h", "ĥ" => "h", "ה" => "h",
        "i" => "i", "ï" => "i", "î" => "i", "í" => "i", "ì" => "i", "į" => "i", "ĭ" => "i", "ı" => "i", "и" => "i", "ĩ" => "i", "ǐ" => "i", "י" => "i", "ї" => "i", "ī" => "i", "і" => "i",
        "й" => "j", "Й" => "j", "Ĵ" => "j", "ĵ" => "j",
        "ĸ" => "k", "כ" => "k", "ķ" => "k", "к" => "k", "ך" => "k",
        "ł" => "l", "ŀ" => "l", "л" => "l", "ļ" => "l", "ĺ" => "l", "ľ" => "l", "ל" => "l",
        "מ" => "m", "м" => "m", "ם" => "m",
        "ñ" => "n", "ń" => "n", "н" => "n", "ņ" => "n", "ן" => "n", "ŋ" => "n", "נ" => "n", "ʼn" => "n", "ň" => "n",
        "ø" => "o", "ó" => "o", "ò" => "o", "ô" => "o", "õ" => "o", "о" => "o", "ő" => "o", "ŏ" => "o", "ō" => "o", "ǿ" => "o", "ǒ" => "o", "ơ" => "o",
        "פ" => "p", "ף" => "p", "п" => "p",
        "ק" => "q",
        "ŕ" => "r", "ř" => "r", "ŗ" => "r", "ר" => "r", "р" => "r", "®" => "r",
        "ş" => "s", "ś" => "s", "ș" => "s", "š" => "s", "с" => "s", "ŝ" => "s", "ס" => "s",
        "т" => "t", "ț" => "t", "ט" => "t", "ŧ" => "t", "ת" => "t", "ť" => "t", "ţ" => "t",
        "ù" => "u", "û" => "u", "ú" => "u", "ū" => "u", "у" => "u", "ũ" => "u", "ư" => "u", "ǔ" => "u", "ų" => "u", "ŭ" => "u", "ů" => "u", "ű" => "u", "ǖ" => "u", "ǜ" => "u", "ǚ" => "u", "ǘ" => "u",
        "в" => "v", "ו" => "v",
        "ý" => "y", "ы" => "y", "ŷ" => "y", "ÿ" => "y",
        "ź" => "z", "ž" => "z", "ż" => "z", "з" => "z", "ז" => "z", "ſ" => "z",
        "™" => "tm",
        "@" => "at",
        "Ä" => "ae", "Ǽ" => "ae", "ä" => "ae", "æ" => "ae", "ǽ" => "ae",
        "ij" => "ij", "IJ" => "ij",
        "я" => "ja", "Я" => "ja",
        "Э" => "je", "э" => "je",
        "ё" => "jo", "Ё" => "jo",
        "ю" => "ju", "Ю" => "ju",
        "œ" => "oe", "Œ" => "oe", "ö" => "oe", "Ö" => "oe",
        "щ" => "sch", "Щ" => "sch",
        "ш" => "sh", "Ш" => "sh",
        "ß" => "ss",
        "Ü" => "ue",
        "Ж" => "zh", "ж" => "zh",
    );
    return strtr($subject, $char_map);
}

$string = "Ħí ŧħə®ë, юßť å test!";
echo replace_spec_char($string);

Ħí ŧħə®ë, юßť å test! => Hi there, jusst a test!

Esto no mezcla caracteres en mayúsculas y minúsculas excepto para caracteres más largos (por ejemplo: ss, ch, sch), agregado @ ® ©

Además, si desea crear una coincidencia de expresiones regulares independientemente de los caracteres especiales:

rss => '[rŕřŘŗŖרŔРр](?:[sșсŜšśסşСŝ][sșсŜšśסşСŝ]|[ß])'

Una implementación de vala de esto: https://code.launchpad.net/~jeremy-munsch/synapse-project/ascii-smart/+merge/277477

Aquí está la lista base con la que podría trabajar, con el reemplazo de expresiones regulares (en texto sublime) o un pequeño script, puede construir cualquier cosa a partir de esta matriz para satisfacer sus necesidades.

"-" => "ъьЪЬ",
"A" => "АĂǍĄÀÃÁÆÂÅǺĀא",
"B" => "БבÞ",
"C" => "ĈĆÇЦצĊČ©ץ",
"D" => "ДĎĐדÐ",
"E" => "ÈĘÉËÊЕĒĖĚĔЄƏע",
"F" => "ФƑ",
"G" => "ĞĠĢĜГגҐ",
"H" => "חĦХĤה",
"I" => "IÏÎÍÌĮĬIИĨǏיЇĪІ",
"J" => "ЙĴ",
"K" => "ĸכĶКך",
"L" => "ŁĿЛĻĹĽל",
"M" => "מМם",
"N" => "ÑŃНŅןŊנʼnŇ",
"O" => "ØÓÒÔÕОŐŎŌǾǑƠ",
"P" => "פףП",
"Q" => "ק",
"R" => "ŔŘŖרР®",
"S" => "ŞŚȘŠСŜס",
"T" => "ТȚטŦתŤŢ",
"U" => "ÙÛÚŪУŨƯǓŲŬŮŰǕǛǙǗ",
"V" => "Вו",
"Y" => "ÝЫŶŸ",
"Z" => "ŹŽŻЗז",
"a" => "аăǎąàãáæâåǻāא",
"b" => "бבþ",
"c" => "ĉćçцצċč©ץ",
"ch" => "ч",
"d" => "дďđדð",
"e" => "èęéëêеēėěĕєəע",
"f" => "фƒ",
"g" => "ğġģĝгגґ",
"h" => "חħхĥה",
"i" => "iïîíìįĭıиĩǐיїīі",
"j" => "йĵ",
"k" => "ĸכķкך",
"l" => "łŀлļĺľל",
"m" => "מмם",
"n" => "ñńнņןŋנʼnň",
"o" => "øóòôõоőŏōǿǒơ",
"p" => "פףп",
"q" => "ק",
"r" => "ŕřŗרр®",
"s" => "şśșšсŝס",
"t" => "тțטŧתťţ",
"u" => "ùûúūуũưǔųŭůűǖǜǚǘ",
"v" => "вו",
"y" => "ýыŷÿ",
"z" => "źžżзזſ",
"tm" => "™",
"at" => "@",
"ae" => "ÄǼäæǽ",
"ch" => "Чч",
"ij" => "ijIJ",
"j" => "йЙĴĵ",
"ja" => "яЯ",
"je" => "Ээ",
"jo" => "ёЁ",
"ju" => "юЮ",
"oe" => "œŒöÖ",
"sch" => "щЩ",
"sh" => "шШ",
"ss" => "ß",
"tm" => "™",
"ue" => "Ü",
"zh" => "Жж"

protected $_convertTable = array(
    '&' => 'and',   '@' => 'at',    '©' => 'c', '®' => 'r', 'À' => 'a',
    'Á' => 'a', 'Â' => 'a', 'Ä' => 'a', 'Å' => 'a', 'Æ' => 'ae','Ç' => 'c',
    'È' => 'e', 'É' => 'e', 'Ë' => 'e', 'Ì' => 'i', 'Í' => 'i', 'Î' => 'i',
    'Ï' => 'i', 'Ò' => 'o', 'Ó' => 'o', 'Ô' => 'o', 'Õ' => 'o', 'Ö' => 'o',
    'Ø' => 'o', 'Ù' => 'u', 'Ú' => 'u', 'Û' => 'u', 'Ü' => 'u', 'Ý' => 'y',
    'ß' => 'ss','à' => 'a', 'á' => 'a', 'â' => 'a', 'ä' => 'a', 'å' => 'a',
    'æ' => 'ae','ç' => 'c', 'è' => 'e', 'é' => 'e', 'ê' => 'e', 'ë' => 'e',
    'ì' => 'i', 'í' => 'i', 'î' => 'i', 'ï' => 'i', 'ò' => 'o', 'ó' => 'o',
    'ô' => 'o', 'õ' => 'o', 'ö' => 'o', 'ø' => 'o', 'ù' => 'u', 'ú' => 'u',
    'û' => 'u', 'ü' => 'u', 'ý' => 'y', 'þ' => 'p', 'ÿ' => 'y', 'Ā' => 'a',
    'ā' => 'a', 'Ă' => 'a', 'ă' => 'a', 'Ą' => 'a', 'ą' => 'a', 'Ć' => 'c',
    'ć' => 'c', 'Ĉ' => 'c', 'ĉ' => 'c', 'Ċ' => 'c', 'ċ' => 'c', 'Č' => 'c',
    'č' => 'c', 'Ď' => 'd', 'ď' => 'd', 'Đ' => 'd', 'đ' => 'd', 'Ē' => 'e',
    'ē' => 'e', 'Ĕ' => 'e', 'ĕ' => 'e', 'Ė' => 'e', 'ė' => 'e', 'Ę' => 'e',
    'ę' => 'e', 'Ě' => 'e', 'ě' => 'e', 'Ĝ' => 'g', 'ĝ' => 'g', 'Ğ' => 'g',
    'ğ' => 'g', 'Ġ' => 'g', 'ġ' => 'g', 'Ģ' => 'g', 'ģ' => 'g', 'Ĥ' => 'h',
    'ĥ' => 'h', 'Ħ' => 'h', 'ħ' => 'h', 'Ĩ' => 'i', 'ĩ' => 'i', 'Ī' => 'i',
    'ī' => 'i', 'Ĭ' => 'i', 'ĭ' => 'i', 'Į' => 'i', 'į' => 'i', 'İ' => 'i',
    'ı' => 'i', 'IJ' => 'ij','ij' => 'ij','Ĵ' => 'j', 'ĵ' => 'j', 'Ķ' => 'k',
    'ķ' => 'k', 'ĸ' => 'k', 'Ĺ' => 'l', 'ĺ' => 'l', 'Ļ' => 'l', 'ļ' => 'l',
    'Ľ' => 'l', 'ľ' => 'l', 'Ŀ' => 'l', 'ŀ' => 'l', 'Ł' => 'l', 'ł' => 'l',
    'Ń' => 'n', 'ń' => 'n', 'Ņ' => 'n', 'ņ' => 'n', 'Ň' => 'n', 'ň' => 'n',
    'ʼn' => 'n', 'Ŋ' => 'n', 'ŋ' => 'n', 'Ō' => 'o', 'ō' => 'o', 'Ŏ' => 'o',
    'ŏ' => 'o', 'Ő' => 'o', 'ő' => 'o', 'Œ' => 'oe','œ' => 'oe','Ŕ' => 'r',
    'ŕ' => 'r', 'Ŗ' => 'r', 'ŗ' => 'r', 'Ř' => 'r', 'ř' => 'r', 'Ś' => 's',
    'ś' => 's', 'Ŝ' => 's', 'ŝ' => 's', 'Ş' => 's', 'ş' => 's', 'Š' => 's',
    'š' => 's', 'Ţ' => 't', 'ţ' => 't', 'Ť' => 't', 'ť' => 't', 'Ŧ' => 't',
    'ŧ' => 't', 'Ũ' => 'u', 'ũ' => 'u', 'Ū' => 'u', 'ū' => 'u', 'Ŭ' => 'u',
    'ŭ' => 'u', 'Ů' => 'u', 'ů' => 'u', 'Ű' => 'u', 'ű' => 'u', 'Ų' => 'u',
    'ų' => 'u', 'Ŵ' => 'w', 'ŵ' => 'w', 'Ŷ' => 'y', 'ŷ' => 'y', 'Ÿ' => 'y',
    'Ź' => 'z', 'ź' => 'z', 'Ż' => 'z', 'ż' => 'z', 'Ž' => 'z', 'ž' => 'z',
    'ſ' => 'z', 'Ə' => 'e', 'ƒ' => 'f', 'Ơ' => 'o', 'ơ' => 'o', 'Ư' => 'u',
    'ư' => 'u', 'Ǎ' => 'a', 'ǎ' => 'a', 'Ǐ' => 'i', 'ǐ' => 'i', 'Ǒ' => 'o',
    'ǒ' => 'o', 'Ǔ' => 'u', 'ǔ' => 'u', 'Ǖ' => 'u', 'ǖ' => 'u', 'Ǘ' => 'u',
    'ǘ' => 'u', 'Ǚ' => 'u', 'ǚ' => 'u', 'Ǜ' => 'u', 'ǜ' => 'u', 'Ǻ' => 'a',
    'ǻ' => 'a', 'Ǽ' => 'ae','ǽ' => 'ae','Ǿ' => 'o', 'ǿ' => 'o', 'ə' => 'e',
    'Ё' => 'jo','Є' => 'e', 'І' => 'i', 'Ї' => 'i', 'А' => 'a', 'Б' => 'b',
    'В' => 'v', 'Г' => 'g', 'Д' => 'd', 'Е' => 'e', 'Ж' => 'zh','З' => 'z',
    'И' => 'i', 'Й' => 'j', 'К' => 'k', 'Л' => 'l', 'М' => 'm', 'Н' => 'n',
    'О' => 'o', 'П' => 'p', 'Р' => 'r', 'С' => 's', 'Т' => 't', 'У' => 'u',
    'Ф' => 'f', 'Х' => 'h', 'Ц' => 'c', 'Ч' => 'ch','Ш' => 'sh','Щ' => 'sch',
    'Ъ' => '-', 'Ы' => 'y', 'Ь' => '-', 'Э' => 'je','Ю' => 'ju','Я' => 'ja',
    'а' => 'a', 'б' => 'b', 'в' => 'v', 'г' => 'g', 'д' => 'd', 'е' => 'e',
    'ж' => 'zh','з' => 'z', 'и' => 'i', 'й' => 'j', 'к' => 'k', 'л' => 'l',
    'м' => 'm', 'н' => 'n', 'о' => 'o', 'п' => 'p', 'р' => 'r', 'с' => 's',
    'т' => 't', 'у' => 'u', 'ф' => 'f', 'х' => 'h', 'ц' => 'c', 'ч' => 'ch',
    'ш' => 'sh','щ' => 'sch','ъ' => '-','ы' => 'y', 'ь' => '-', 'э' => 'je',
    'ю' => 'ju','я' => 'ja','ё' => 'jo','є' => 'e', 'і' => 'i', 'ї' => 'i',
    'Ґ' => 'g', 'ґ' => 'g', 'א' => 'a', 'ב' => 'b', 'ג' => 'g', 'ד' => 'd',
    'ה' => 'h', 'ו' => 'v', 'ז' => 'z', 'ח' => 'h', 'ט' => 't', 'י' => 'i',
    'ך' => 'k', 'כ' => 'k', 'ל' => 'l', 'ם' => 'm', 'מ' => 'm', 'ן' => 'n',
    'נ' => 'n', 'ס' => 's', 'ע' => 'e', 'ף' => 'p', 'פ' => 'p', 'ץ' => 'C',
    'צ' => 'c', 'ק' => 'q', 'ר' => 'r', 'ש' => 'w', 'ת' => 't', '™' => 'tm',
);

De magento, lo estoy usando básicamente para todo

si tiene http://php.net/manual/en/book.intl.php disponible, esto resolverá su problema:

$string = "Éric Cantona";
$transliterator = Transliterator::createFromRules(':: NFD; :: [:Nonspacing Mark:] Remove; :: Lower(); :: NFC;', Transliterator::FORWARD);
echo $normalized = $transliterator->transliterate($string);

EDITAR

Para instalar la extensión php en ubuntu:

apt-get install php-intl

No olvide, en Composer, solicitar la extensión ext-intlpara asegurarse de que se ajuste correctamente a los sistemas implementados.

Descargo de responsabilidad: ya no apoyo esta respuesta (estaba ciego en ese momento). Pero gracias por los votos positivos = P

Puedes tomar esto como base. Desde WordPress, utilizado para generar URL bonitas (el punto de entrada es la función slugify ()):

/**
 * Converts all accent characters to ASCII characters.
 *
 * If there are no accent characters, then the string given is just returned.
 *
 * @param string $string Text that might have accent characters
 * @return string Filtered string with replaced "nice" characters.
 */

function remove_accents($string) {
 if (!preg_match('/[\x80-\xff]/', $string))
  return $string;
 if (seems_utf8($string)) {
  $chars = array(
  // Decompositions for Latin-1 Supplement
  chr(195).chr(128) => 'A', chr(195).chr(129) => 'A',
  chr(195).chr(130) => 'A', chr(195).chr(131) => 'A',
  chr(195).chr(132) => 'A', chr(195).chr(133) => 'A',
  chr(195).chr(135) => 'C', chr(195).chr(136) => 'E',
  chr(195).chr(137) => 'E', chr(195).chr(138) => 'E',
  chr(195).chr(139) => 'E', chr(195).chr(140) => 'I',
  chr(195).chr(141) => 'I', chr(195).chr(142) => 'I',
  chr(195).chr(143) => 'I', chr(195).chr(145) => 'N',
  chr(195).chr(146) => 'O', chr(195).chr(147) => 'O',
  chr(195).chr(148) => 'O', chr(195).chr(149) => 'O',
  chr(195).chr(150) => 'O', chr(195).chr(153) => 'U',
  chr(195).chr(154) => 'U', chr(195).chr(155) => 'U',
  chr(195).chr(156) => 'U', chr(195).chr(157) => 'Y',
  chr(195).chr(159) => 's', chr(195).chr(160) => 'a',
  chr(195).chr(161) => 'a', chr(195).chr(162) => 'a',
  chr(195).chr(163) => 'a', chr(195).chr(164) => 'a',
  chr(195).chr(165) => 'a', chr(195).chr(167) => 'c',
  chr(195).chr(168) => 'e', chr(195).chr(169) => 'e',
  chr(195).chr(170) => 'e', chr(195).chr(171) => 'e',
  chr(195).chr(172) => 'i', chr(195).chr(173) => 'i',
  chr(195).chr(174) => 'i', chr(195).chr(175) => 'i',
  chr(195).chr(177) => 'n', chr(195).chr(178) => 'o',
  chr(195).chr(179) => 'o', chr(195).chr(180) => 'o',
  chr(195).chr(181) => 'o', chr(195).chr(182) => 'o',
  chr(195).chr(182) => 'o', chr(195).chr(185) => 'u',
  chr(195).chr(186) => 'u', chr(195).chr(187) => 'u',
  chr(195).chr(188) => 'u', chr(195).chr(189) => 'y',
  chr(195).chr(191) => 'y',
  // Decompositions for Latin Extended-A
  chr(196).chr(128) => 'A', chr(196).chr(129) => 'a',
  chr(196).chr(130) => 'A', chr(196).chr(131) => 'a',
  chr(196).chr(132) => 'A', chr(196).chr(133) => 'a',
  chr(196).chr(134) => 'C', chr(196).chr(135) => 'c',
  chr(196).chr(136) => 'C', chr(196).chr(137) => 'c',
  chr(196).chr(138) => 'C', chr(196).chr(139) => 'c',
  chr(196).chr(140) => 'C', chr(196).chr(141) => 'c',
  chr(196).chr(142) => 'D', chr(196).chr(143) => 'd',
  chr(196).chr(144) => 'D', chr(196).chr(145) => 'd',
  chr(196).chr(146) => 'E', chr(196).chr(147) => 'e',
  chr(196).chr(148) => 'E', chr(196).chr(149) => 'e',
  chr(196).chr(150) => 'E', chr(196).chr(151) => 'e',
  chr(196).chr(152) => 'E', chr(196).chr(153) => 'e',
  chr(196).chr(154) => 'E', chr(196).chr(155) => 'e',
  chr(196).chr(156) => 'G', chr(196).chr(157) => 'g',
  chr(196).chr(158) => 'G', chr(196).chr(159) => 'g',
  chr(196).chr(160) => 'G', chr(196).chr(161) => 'g',
  chr(196).chr(162) => 'G', chr(196).chr(163) => 'g',
  chr(196).chr(164) => 'H', chr(196).chr(165) => 'h',
  chr(196).chr(166) => 'H', chr(196).chr(167) => 'h',
  chr(196).chr(168) => 'I', chr(196).chr(169) => 'i',
  chr(196).chr(170) => 'I', chr(196).chr(171) => 'i',
  chr(196).chr(172) => 'I', chr(196).chr(173) => 'i',
  chr(196).chr(174) => 'I', chr(196).chr(175) => 'i',
  chr(196).chr(176) => 'I', chr(196).chr(177) => 'i',
  chr(196).chr(178) => 'IJ',chr(196).chr(179) => 'ij',
  chr(196).chr(180) => 'J', chr(196).chr(181) => 'j',
  chr(196).chr(182) => 'K', chr(196).chr(183) => 'k',
  chr(196).chr(184) => 'k', chr(196).chr(185) => 'L',
  chr(196).chr(186) => 'l', chr(196).chr(187) => 'L',
  chr(196).chr(188) => 'l', chr(196).chr(189) => 'L',
  chr(196).chr(190) => 'l', chr(196).chr(191) => 'L',
  chr(197).chr(128) => 'l', chr(197).chr(129) => 'L',
  chr(197).chr(130) => 'l', chr(197).chr(131) => 'N',
  chr(197).chr(132) => 'n', chr(197).chr(133) => 'N',
  chr(197).chr(134) => 'n', chr(197).chr(135) => 'N',
  chr(197).chr(136) => 'n', chr(197).chr(137) => 'N',
  chr(197).chr(138) => 'n', chr(197).chr(139) => 'N',
  chr(197).chr(140) => 'O', chr(197).chr(141) => 'o',
  chr(197).chr(142) => 'O', chr(197).chr(143) => 'o',
  chr(197).chr(144) => 'O', chr(197).chr(145) => 'o',
  chr(197).chr(146) => 'OE',chr(197).chr(147) => 'oe',
  chr(197).chr(148) => 'R',chr(197).chr(149) => 'r',
  chr(197).chr(150) => 'R',chr(197).chr(151) => 'r',
  chr(197).chr(152) => 'R',chr(197).chr(153) => 'r',
  chr(197).chr(154) => 'S',chr(197).chr(155) => 's',
  chr(197).chr(156) => 'S',chr(197).chr(157) => 's',
  chr(197).chr(158) => 'S',chr(197).chr(159) => 's',
  chr(197).chr(160) => 'S', chr(197).chr(161) => 's',
  chr(197).chr(162) => 'T', chr(197).chr(163) => 't',
  chr(197).chr(164) => 'T', chr(197).chr(165) => 't',
  chr(197).chr(166) => 'T', chr(197).chr(167) => 't',
  chr(197).chr(168) => 'U', chr(197).chr(169) => 'u',
  chr(197).chr(170) => 'U', chr(197).chr(171) => 'u',
  chr(197).chr(172) => 'U', chr(197).chr(173) => 'u',
  chr(197).chr(174) => 'U', chr(197).chr(175) => 'u',
  chr(197).chr(176) => 'U', chr(197).chr(177) => 'u',
  chr(197).chr(178) => 'U', chr(197).chr(179) => 'u',
  chr(197).chr(180) => 'W', chr(197).chr(181) => 'w',
  chr(197).chr(182) => 'Y', chr(197).chr(183) => 'y',
  chr(197).chr(184) => 'Y', chr(197).chr(185) => 'Z',
  chr(197).chr(186) => 'z', chr(197).chr(187) => 'Z',
  chr(197).chr(188) => 'z', chr(197).chr(189) => 'Z',
  chr(197).chr(190) => 'z', chr(197).chr(191) => 's',
  // Euro Sign
  chr(226).chr(130).chr(172) => 'E',
  // GBP (Pound) Sign
  chr(194).chr(163) => '');
  $string = strtr($string, $chars);
 } else {
  // Assume ISO-8859-1 if not UTF-8
  $chars['in'] = chr(128).chr(131).chr(138).chr(142).chr(154).chr(158)
   .chr(159).chr(162).chr(165).chr(181).chr(192).chr(193).chr(194)
   .chr(195).chr(196).chr(197).chr(199).chr(200).chr(201).chr(202)
   .chr(203).chr(204).chr(205).chr(206).chr(207).chr(209).chr(210)
   .chr(211).chr(212).chr(213).chr(214).chr(216).chr(217).chr(218)
   .chr(219).chr(220).chr(221).chr(224).chr(225).chr(226).chr(227)
   .chr(228).chr(229).chr(231).chr(232).chr(233).chr(234).chr(235)
   .chr(236).chr(237).chr(238).chr(239).chr(241).chr(242).chr(243)
   .chr(244).chr(245).chr(246).chr(248).chr(249).chr(250).chr(251)
   .chr(252).chr(253).chr(255);
  $chars['out'] = "EfSZszYcYuAAAAAACEEEEIIIINOOOOOOUUUUYaaaaaaceeeeiiiinoooooouuuuyy";
  $string = strtr($string, $chars['in'], $chars['out']);
  $double_chars['in'] = array(chr(140), chr(156), chr(198), chr(208), chr(222), chr(223), chr(230), chr(240), chr(254));
  $double_chars['out'] = array('OE', 'oe', 'AE', 'DH', 'TH', 'ss', 'ae', 'dh', 'th');
  $string = str_replace($double_chars['in'], $double_chars['out'], $string);
 }
 return $string;
}

/**
 * Checks to see if a string is utf8 encoded.
 *
 * @author bmorel at ssi dot fr
 *
 * @param string $Str The string to be checked
 * @return bool True if $Str fits a UTF-8 model, false otherwise.
 */
function seems_utf8($Str) { # by bmorel at ssi dot fr
 $length = strlen($Str);
 for ($i = 0; $i < $length; $i++) {
  if (ord($Str[$i]) < 0x80) continue; # 0bbbbbbb
  elseif ((ord($Str[$i]) & 0xE0) == 0xC0) $n = 1; # 110bbbbb
  elseif ((ord($Str[$i]) & 0xF0) == 0xE0) $n = 2; # 1110bbbb
  elseif ((ord($Str[$i]) & 0xF8) == 0xF0) $n = 3; # 11110bbb
  elseif ((ord($Str[$i]) & 0xFC) == 0xF8) $n = 4; # 111110bb
  elseif ((ord($Str[$i]) & 0xFE) == 0xFC) $n = 5; # 1111110b
  else return false; # Does not match any model
  for ($j = 0; $j < $n; $j++) { # n bytes matching 10bbbbbb follow ?
   if ((++$i == $length) || ((ord($Str[$i]) & 0xC0) != 0x80))
   return false;
  }
 }
 return true;
}

function utf8_uri_encode($utf8_string, $length = 0) {
 $unicode = '';
 $values = array();
 $num_octets = 1;
 $unicode_length = 0;
 $string_length = strlen($utf8_string);
 for ($i = 0; $i < $string_length; $i++) {
  $value = ord($utf8_string[$i]);
  if ($value < 128) {
   if ($length && ($unicode_length >= $length))
    break;
   $unicode .= chr($value);
   $unicode_length++;
  } else {
   if (count($values) == 0) $num_octets = ($value < 224) ? 2 : 3;
   $values[] = $value;
   if ($length && ($unicode_length + ($num_octets * 3)) > $length)
    break;
   if (count( $values ) == $num_octets) {
    if ($num_octets == 3) {
     $unicode .= '%' . dechex($values[0]) . '%' . dechex($values[1]) . '%' . dechex($values[2]);
     $unicode_length += 9;
    } else {
     $unicode .= '%' . dechex($values[0]) . '%' . dechex($values[1]);
     $unicode_length += 6;
    }
    $values = array();
    $num_octets = 1;
   }
  }
 }
 return $unicode;
}

/**
 * Sanitizes title, replacing whitespace with dashes.
 *
 * Limits the output to alphanumeric characters, underscore (_) and dash (-).
 * Whitespace becomes a dash.
 *
 * @param string $title The title to be sanitized.
 * @return string The sanitized title.
 */
function slugify($title) {
 $title = strip_tags($title);
 // Preserve escaped octets.
 $title = preg_replace('|%([a-fA-F0-9][a-fA-F0-9])|', '---$1---', $title);
 // Remove percent signs that are not part of an octet.
 $title = str_replace('%', '', $title);
 // Restore octets.
 $title = preg_replace('|---([a-fA-F0-9][a-fA-F0-9])---|', '%$1', $title);
 $title = remove_accents($title);
 if (seems_utf8($title)) {
  if (function_exists('mb_strtolower')) {
   $title = mb_strtolower($title, 'UTF-8');
  }
  $title = utf8_uri_encode($title, 200);
 }
 $title = strtolower($title);
 $title = preg_replace('/&.+?;/', '', $title); // kill entities
 $title = preg_replace('/[^%a-z0-9 _-]/', '', $title);
 $title = preg_replace('/\s+/', '-', $title);
 $title = preg_replace('|-+|', '-', $title);
 $title = trim($title, '-');
 return $title;
}

He buscado y su idea para el marcado de acento es bastante impresionante y rentable, pero su expresión regular está mal hecha y pierde 2 parámetros adicionales. En pocas palabras, la expresión regular debe ser:

$patterns[0] = '/[áâàåä]/ui';
$patterns[1] = '/[ðéêèë]/ui';
$patterns[2] = '/[íîìï]/ui';
$patterns[3] = '/[óôòøõö]/ui';
$patterns[4] = '/[úûùü]/ui';
$patterns[5] = '/æ/ui';
$patterns[6] = '/ç/ui';
$patterns[7] = '/ß/ui';
$replacements[0] = 'a';
$replacements[1] = 'e';
$replacements[2] = 'i';
$replacements[3] = 'o';
$replacements[4] = 'u';
$replacements[5] = 'ae';
$replacements[6] = 'c';
$replacements[7] = 'ss';

Como puede ver es bastante similar pero lo más importante son los paramas después de la segunda barra de la expresión regular. Cuando una expresión regualr es así /[someCoolRegex]/uilas uespecifica que se debe utilizar Unicode y los iespecifica que es sensible a mayúsculas, He probado mi propia y con la ansewer en este foro hay que decir es más Efectiva costo de utilizar strtr.

Espero que alguien lea esta respuesta.

strtolowersolo funciona en cadenas codificadas con iso-8859-1. Podrías probar con mb_strtolower.

O, si tiene que modificar con extensiones multibyte, también puede usar el soporte de transliteración de iconv:

iconv("UTF-8", "ISO-8859-1//TRANSLIT", $text);

Editar:

Parece que fui un poco rápido. Parece que usa iso-8859-1, por lo que su estrategia actual funcionará. Solo necesita escribir las expresiones regulares correctamente. P.ej.:

'/(ð|é|ê|è|ë)/'

no:

'/[ð|é|ê|è|ë]/'

Puede usar la función PHP strtr () para deshacerse de los caracteres acentuados:

$string = "Éric Cantona";
$accented_array = array('Š'=>'S', 'š'=>'s', 'Ž'=>'Z', 'ž'=>'z', 'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E','Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U','Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss', 'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c','è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o','ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'þ'=>'b', 'ÿ'=>'y' );

$required_str = strtr( $string, $accented_array );

Lo sé, esa pregunta se ha hecho hace mucho tiempo ...

Estaba buscando una solución corta y elegante, pero no pude encontrar satisfacción por dos razones:

Primero, la mayoría de las soluciones existentes reemplazan una lista de personajes por una lista de otros personajes. Desafortunadamente, requiere usar una codificación específica para el archivo de script php en sí, lo que podría no ser deseado.

En segundo lugar, usar iconv parece ser una buena forma, pero no es suficiente, ya que el resultado de un personaje convertido podría ser uno o dos caracteres, o una Excepción fatal.

Entonces escribí esa pequeña función que hace el trabajo:

function replaceAccent($string, $replacement = '_')
{
    $alnumPattern = '/^[a-zA-Z0-9 ]+$/';

    if (preg_match($alnumPattern, $string)) {
        return $string;
    }

    $ret = array_map(
        function ($chr) use ($alnumPattern, $replacement) {
            if (preg_match($alnumPattern, $chr)) {
                return $chr;
            } else {
                $chr = @iconv('ISO-8859-1', 'ASCII//TRANSLIT', $chr);
                if (strlen($chr) == 1) {
                    return $chr;
                } elseif (strlen($chr) > 1) {
                    $ret = '';
                    foreach (str_split($chr) as $char2) {
                        if (preg_match($alnumPattern, $char2)) {
                            $ret .= $char2;
                        }
                    }
                    return $ret;
                } else {
                    // replace whatever iconv fail to convert by something else
                    return $replacement;
                }
            }
        },
        str_split($string)
    );

    return implode($ret);
}

Como alternativa (un poco más compleja por naturaleza), eche un vistazo a cómo wordpress elimina el acento. Hice algunos cambios a continuación para que se ejecute de forma independiente sin hacer referencia a las funciones de WordPress.

     function mbstring_binary_safe_encoding($reset = false)
{
    static $encodings  = array();
    static $overloaded = null;

    if (is_null($overloaded)) {
        $overloaded = function_exists('mb_internal_encoding') && (ini_get('mbstring.func_overload') & 2);
    }

    if (false === $overloaded) {
        return;
    }

    if (!$reset) {
        $encoding = mb_internal_encoding();
        array_push($encodings, $encoding);
        mb_internal_encoding('ISO-8859-1');
    }

    if ($reset && $encodings) {
        $encoding = array_pop($encodings);
        mb_internal_encoding($encoding);
    }
}

function seems_utf8($str)
{
    mbstring_binary_safe_encoding();
    $length = strlen($str);
    mbstring_binary_safe_encoding(true);
    for ($i = 0; $i < $length; $i++) {
        $c = ord($str[$i]);
        if ($c < 0x80) {
            $n = 0;
        }
        // 0bbbbbbb
        elseif (($c & 0xE0) == 0xC0) {
            $n = 1;
        }
        // 110bbbbb
        elseif (($c & 0xF0) == 0xE0) {
            $n = 2;
        }
        // 1110bbbb
        elseif (($c & 0xF8) == 0xF0) {
            $n = 3;
        }
        // 11110bbb
        elseif (($c & 0xFC) == 0xF8) {
            $n = 4;
        }
        // 111110bb
        elseif (($c & 0xFE) == 0xFC) {
            $n = 5;
        }
        // 1111110b
        else {
                return false;
            }
            // Does not match any model
            for ($j = 0; $j < $n; $j++) {
                // n bytes matching 10bbbbbb follow ?
                if ((++$i == $length) || ((ord($str[$i]) & 0xC0) != 0x80)) {
                    return false;
                }

            }
        }
        return true;
    }

    function remove_accents($string)
{
        if (!preg_match('/[\x80-\xff]/', $string)) {
            return $string;
        }

        if (seems_utf8($string)) {
            $chars = array(
                // Decompositions for Latin-1 Supplement
                'ª' => 'a', 'º'  => 'o',
                'À' => 'A', 'Á'  => 'A',
                'Â' => 'A', 'Ã'  => 'A',
                'Ä' => 'A', 'Å'  => 'A',
                'Æ' => 'AE', 'Ç' => 'C',
                'È' => 'E', 'É'  => 'E',
                'Ê' => 'E', 'Ë'  => 'E',
                'Ì' => 'I', 'Í'  => 'I',
                'Î' => 'I', 'Ï'  => 'I',
                'Ð' => 'D', 'Ñ'  => 'N',
                'Ò' => 'O', 'Ó'  => 'O',
                'Ô' => 'O', 'Õ'  => 'O',
                'Ö' => 'O', 'Ù'  => 'U',
                'Ú' => 'U', 'Û'  => 'U',
                'Ü' => 'U', 'Ý'  => 'Y',
                'Þ' => 'TH', 'ß' => 's',
                'à' => 'a', 'á'  => 'a',
                'â' => 'a', 'ã'  => 'a',
                'ä' => 'a', 'å'  => 'a',
                'æ' => 'ae', 'ç' => 'c',
                'è' => 'e', 'é'  => 'e',
                'ê' => 'e', 'ë'  => 'e',
                'ì' => 'i', 'í'  => 'i',
                'î' => 'i', 'ï'  => 'i',
                'ð' => 'd', 'ñ'  => 'n',
                'ò' => 'o', 'ó'  => 'o',
                'ô' => 'o', 'õ'  => 'o',
                'ö' => 'o', 'ø'  => 'o',
                'ù' => 'u', 'ú'  => 'u',
                'û' => 'u', 'ü'  => 'u',
                'ý' => 'y', 'þ'  => 'th',
                'ÿ' => 'y', 'Ø'  => 'O',
                // Decompositions for Latin Extended-A
                'Ā' => 'A', 'ā'  => 'a',
                'Ă' => 'A', 'ă'  => 'a',
                'Ą' => 'A', 'ą'  => 'a',
                'Ć' => 'C', 'ć'  => 'c',
                'Ĉ' => 'C', 'ĉ'  => 'c',
                'Ċ' => 'C', 'ċ'  => 'c',
                'Č' => 'C', 'č'  => 'c',
                'Ď' => 'D', 'ď'  => 'd',
                'Đ' => 'D', 'đ'  => 'd',
                'Ē' => 'E', 'ē'  => 'e',
                'Ĕ' => 'E', 'ĕ'  => 'e',
                'Ė' => 'E', 'ė'  => 'e',
                'Ę' => 'E', 'ę'  => 'e',
                'Ě' => 'E', 'ě'  => 'e',
                'Ĝ' => 'G', 'ĝ'  => 'g',
                'Ğ' => 'G', 'ğ'  => 'g',
                'Ġ' => 'G', 'ġ'  => 'g',
                'Ģ' => 'G', 'ģ'  => 'g',
                'Ĥ' => 'H', 'ĥ'  => 'h',
                'Ħ' => 'H', 'ħ'  => 'h',
                'Ĩ' => 'I', 'ĩ'  => 'i',
                'Ī' => 'I', 'ī'  => 'i',
                'Ĭ' => 'I', 'ĭ'  => 'i',
                'Į' => 'I', 'į'  => 'i',
                'İ' => 'I', 'ı'  => 'i',
                'IJ' => 'IJ', 'ij' => 'ij',
                'Ĵ' => 'J', 'ĵ'  => 'j',
                'Ķ' => 'K', 'ķ'  => 'k',
                'ĸ' => 'k', 'Ĺ'  => 'L',
                'ĺ' => 'l', 'Ļ'  => 'L',
                'ļ' => 'l', 'Ľ'  => 'L',
                'ľ' => 'l', 'Ŀ'  => 'L',
                'ŀ' => 'l', 'Ł'  => 'L',
                'ł' => 'l', 'Ń'  => 'N',
                'ń' => 'n', 'Ņ'  => 'N',
                'ņ' => 'n', 'Ň'  => 'N',
                'ň' => 'n', 'ʼn'  => 'n',
                'Ŋ' => 'N', 'ŋ'  => 'n',
                'Ō' => 'O', 'ō'  => 'o',
                'Ŏ' => 'O', 'ŏ'  => 'o',
                'Ő' => 'O', 'ő'  => 'o',
                'Œ' => 'OE', 'œ' => 'oe',
                'Ŕ' => 'R', 'ŕ'  => 'r',
                'Ŗ' => 'R', 'ŗ'  => 'r',
                'Ř' => 'R', 'ř'  => 'r',
                'Ś' => 'S', 'ś'  => 's',
                'Ŝ' => 'S', 'ŝ'  => 's',
                'Ş' => 'S', 'ş'  => 's',
                'Š' => 'S', 'š'  => 's',
                'Ţ' => 'T', 'ţ'  => 't',
                'Ť' => 'T', 'ť'  => 't',
                'Ŧ' => 'T', 'ŧ'  => 't',
                'Ũ' => 'U', 'ũ'  => 'u',
                'Ū' => 'U', 'ū'  => 'u',
                'Ŭ' => 'U', 'ŭ'  => 'u',
                'Ů' => 'U', 'ů'  => 'u',
                'Ű' => 'U', 'ű'  => 'u',
                'Ų' => 'U', 'ų'  => 'u',
                'Ŵ' => 'W', 'ŵ'  => 'w',
                'Ŷ' => 'Y', 'ŷ'  => 'y',
                'Ÿ' => 'Y', 'Ź'  => 'Z',
                'ź' => 'z', 'Ż'  => 'Z',
                'ż' => 'z', 'Ž'  => 'Z',
                'ž' => 'z', 'ſ'  => 's',
                // Decompositions for Latin Extended-B
                'Ș' => 'S', 'ș'  => 's',
                'Ț' => 'T', 'ț'  => 't',
                // Euro Sign
                '€' => 'E',
                // GBP (Pound) Sign
                '£' => '',
                // Vowels with diacritic (Vietnamese)
                // unmarked
                'Ơ' => 'O', 'ơ'  => 'o',
                'Ư' => 'U', 'ư'  => 'u',
                // grave accent
                'Ầ' => 'A', 'ầ'  => 'a',
                'Ằ' => 'A', 'ằ'  => 'a',
                'Ề' => 'E', 'ề'  => 'e',
                'Ồ' => 'O', 'ồ'  => 'o',
                'Ờ' => 'O', 'ờ'  => 'o',
                'Ừ' => 'U', 'ừ'  => 'u',
                'Ỳ' => 'Y', 'ỳ'  => 'y',
                // hook
                'Ả' => 'A', 'ả'  => 'a',
                'Ẩ' => 'A', 'ẩ'  => 'a',
                'Ẳ' => 'A', 'ẳ'  => 'a',
                'Ẻ' => 'E', 'ẻ'  => 'e',
                'Ể' => 'E', 'ể'  => 'e',
                'Ỉ' => 'I', 'ỉ'  => 'i',
                'Ỏ' => 'O', 'ỏ'  => 'o',
                'Ổ' => 'O', 'ổ'  => 'o',
                'Ở' => 'O', 'ở'  => 'o',
                'Ủ' => 'U', 'ủ'  => 'u',
                'Ử' => 'U', 'ử'  => 'u',
                'Ỷ' => 'Y', 'ỷ'  => 'y',
                // tilde
                'Ẫ' => 'A', 'ẫ'  => 'a',
                'Ẵ' => 'A', 'ẵ'  => 'a',
                'Ẽ' => 'E', 'ẽ'  => 'e',
                'Ễ' => 'E', 'ễ'  => 'e',
                'Ỗ' => 'O', 'ỗ'  => 'o',
                'Ỡ' => 'O', 'ỡ'  => 'o',
                'Ữ' => 'U', 'ữ'  => 'u',
                'Ỹ' => 'Y', 'ỹ'  => 'y',
                // acute accent
                'Ấ' => 'A', 'ấ'  => 'a',
                'Ắ' => 'A', 'ắ'  => 'a',
                'Ế' => 'E', 'ế'  => 'e',
                'Ố' => 'O', 'ố'  => 'o',
                'Ớ' => 'O', 'ớ'  => 'o',
                'Ứ' => 'U', 'ứ'  => 'u',
                // dot below
                'Ạ' => 'A', 'ạ'  => 'a',
                'Ậ' => 'A', 'ậ'  => 'a',
                'Ặ' => 'A', 'ặ'  => 'a',
                'Ẹ' => 'E', 'ẹ'  => 'e',
                'Ệ' => 'E', 'ệ'  => 'e',
                'Ị' => 'I', 'ị'  => 'i',
                'Ọ' => 'O', 'ọ'  => 'o',
                'Ộ' => 'O', 'ộ'  => 'o',
                'Ợ' => 'O', 'ợ'  => 'o',
                'Ụ' => 'U', 'ụ'  => 'u',
                'Ự' => 'U', 'ự'  => 'u',
                'Ỵ' => 'Y', 'ỵ'  => 'y',
                // Vowels with diacritic (Chinese, Hanyu Pinyin)
                'ɑ' => 'a',
                // macron
                'Ǖ' => 'U', 'ǖ'  => 'u',
                // acute accent
                'Ǘ' => 'U', 'ǘ'  => 'u',
                // caron
                'Ǎ' => 'A', 'ǎ'  => 'a',
                'Ǐ' => 'I', 'ǐ'  => 'i',
                'Ǒ' => 'O', 'ǒ'  => 'o',
                'Ǔ' => 'U', 'ǔ'  => 'u',
                'Ǚ' => 'U', 'ǚ'  => 'u',
                // grave accent
                'Ǜ' => 'U', 'ǜ'  => 'u',
            );

            $string = strtr($string, $chars);
        } else {
            $chars = array();
            // Assume ISO-8859-1 if not UTF-8
            $chars['in'] = "\x80\x83\x8a\x8e\x9a\x9e"
                . "\x9f\xa2\xa5\xb5\xc0\xc1\xc2"
                . "\xc3\xc4\xc5\xc7\xc8\xc9\xca"
                . "\xcb\xcc\xcd\xce\xcf\xd1\xd2"
                . "\xd3\xd4\xd5\xd6\xd8\xd9\xda"
                . "\xdb\xdc\xdd\xe0\xe1\xe2\xe3"
                . "\xe4\xe5\xe7\xe8\xe9\xea\xeb"
                . "\xec\xed\xee\xef\xf1\xf2\xf3"
                . "\xf4\xf5\xf6\xf8\xf9\xfa\xfb"
                . "\xfc\xfd\xff";

            $chars['out'] = "EfSZszYcYuAAAAAACEEEEIIIINOOOOOOUUUUYaaaaaaceeeeiiiinoooooouuuuyy";

            $string              = strtr($string, $chars['in'], $chars['out']);
            $double_chars        = array();
            $double_chars['in']  = array("\x8c", "\x9c", "\xc6", "\xd0", "\xde", "\xdf", "\xe6", "\xf0", "\xfe");
            $double_chars['out'] = array('OE', 'oe', 'AE', 'DH', 'TH', 'ss', 'ae', 'dh', 'th');
            $string              = str_replace($double_chars['in'], $double_chars['out'], $string);
        }

        return $string;
    }

Caracteres vietnamitas para quien los necesite

'Š'=>'S', 'š'=>'s', 'Ž'=>'Z', 'ž'=>'z', 'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E',
                            'Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U',
                            'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss', 'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c',
                            'è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o',
                            'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'þ'=>'b', 'ÿ'=>'y' );
$str = strtr( $str, $unwanted_array );

Encontré que esta manera es buena, sin tener que preocuparme demasiado por conjuntos de caracteres y matrices:

function replace_accents($str) {
   $str = htmlentities($str, ENT_COMPAT, "UTF-8");
   $str = preg_replace('/&([a-zA-Z])(uml|acute|grave|circ|tilde);/','$1',$str);
   return html_entity_decode($str);
}

Puedes probar este

class Diacritic
{
    public function replaceDiacritic($input)
    {
        $input = iconv('UTF-8','ASCII//TRANSLIT',$input);
        $input = preg_replace("/['|^|`|~|]/","",$input);
        $input = preg_replace('/["]/','',$input);
        return preg_replace('/[" "]/','_',$input);
    }
}

Agregando un poco a lo que dijo Lizard , funcionó para mostrarse correctamente en la página web, pero agregó algunos otros códigos para completar lo que estaba buscando, reemplazando mis etiquetas para buscar correctamente en mi base de datos con caracteres especiales. Gracias por adelantado.

$unwanted_array = array(    'Š'=>'S', 'š'=>'s', 'Ž'=>'Z', 'ž'=>'z', 'À'=>'A', 'Á'=>'A', 'Â'=>'A', 'Ã'=>'A', 'Ä'=>'A', 'Å'=>'A', 'Æ'=>'A', 'Ç'=>'C', 'È'=>'E', 'É'=>'E',
                            'Ê'=>'E', 'Ë'=>'E', 'Ì'=>'I', 'Í'=>'I', 'Î'=>'I', 'Ï'=>'I', 'Ñ'=>'N', 'Ò'=>'O', 'Ó'=>'O', 'Ô'=>'O', 'Õ'=>'O', 'Ö'=>'O', 'Ø'=>'O', 'Ù'=>'U',
                            'Ú'=>'U', 'Û'=>'U', 'Ü'=>'U', 'Ý'=>'Y', 'Þ'=>'B', 'ß'=>'Ss', 'à'=>'a', 'á'=>'a', 'â'=>'a', 'ã'=>'a', 'ä'=>'a', 'å'=>'a', 'æ'=>'a', 'ç'=>'c',
                            'è'=>'e', 'é'=>'e', 'ê'=>'e', 'ë'=>'e', 'ì'=>'i', 'í'=>'i', 'î'=>'i', 'ï'=>'i', 'ð'=>'o', 'ñ'=>'n', 'ò'=>'o', 'ó'=>'o', 'ô'=>'o', 'õ'=>'o',
                            'ö'=>'o', 'ø'=>'o', 'ù'=>'u', 'ú'=>'u', 'û'=>'u', 'ý'=>'y', 'þ'=>'b', 'ÿ'=>'y', 
                            'á'=>'a', 'é'=>'e', 'í'=>'i', 'ó'=>'o', 'ú'=>'u',  
                            'Á'=>'A', 'É'=>'E', 'Í'=>'I', 'Ó'=>'O', 'Ú'=>'U',
                            'Ñ'=>'N', 'ñ'=>'n' );
$newtag = strtr( $newtag, $unwanted_array );