PHP でアクセント付きの文字をアクセントのない対応する文字に適切に置き換える方法は?

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

$patterns = [
    '/[á|â|à|å|ä]/',
    '/[ð|é|ê|è|ë]/',
    '/[í|îì|ï]/',
    '/[ó|ô|ò|ø|õ|ö]/',
    '/[ú|û|ù|ü]/',
    '/æ/',
    '/ç/',
    '/ß/'
];

$replacements = [
    'a',
    'e',
    'i',
    'o',
    'u',
    'ae',
    'c',
    'ss'
];

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

$unwanted_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);