Automatically remove emoji from post slug in WordPress

Question

I've a problem on the website of a client.

It's a WordPress website with a permalink structure like this : https://client-domain.com/%category%/%postname%/

WordPress auto-generate post slug from post title after removing some special characters like single quotes for obvious reason, but not emojis.

My client use emojis on almost every post title and I showed him how to edit manually the permalink after its generation but it's not convenient...

Is there a built-in function to automatically remove emoji form slugs ?
Or should I create one, hooked on wp_unique_post_slug ?
(If so, I'll share the code here if anyone need it too)

Answer 1

I've found a solution taking the problem from the other end : keep only "authorized" characters and remove any other (so, including emojis).

The code can be improved and adapted according needs.
The $normalize array part come from this answer to another question

function normalize_url($url) {
    // Character normalizer array
    $normalize = 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',
        '\''=>'-', '_'=>'-', ' '=>'-',':'=>'-',
        '€'=>'-eur-', '$'=>'-dol-', '£'=>'-p-','¥'=>'-y-'
    );

    // Use character normalizer
    $url = strtr($url, $normalize);

    // String to lowercase
    $url = strtolower($url);

    // Replace multiple dash by only one
    $duplicate_dash = "/[\-]{2}/";
    while (preg_match($duplicate_dash, $url)) {
        $url = preg_replace($duplicate_dash, '-', $url);
    }

    // Remove all characters non-matching the defined pattern
    $pattern = "/[^a-z0-9\_\-]/";
    while (preg_match($pattern, $url)) {
        $url = preg_replace($pattern, '', $url);
    }

    // Remove dash at begining and end of string
    while (strpos($url, "-") == 0) {
        $url = substr($url, 1);
    }
    while (substr($url, -1) == '-') {
        $url = substr_replace($url ,"",-1);
    }

    // Return clean URL
    return $url;
}

Any code simplification is welcome !