$re = '~[^A-Za-z0-9.@/ _\xe9\x{e8}-]~u';
$str = 'J\'utilise la commande suivante pour supprimer tous les caractères spéciaux des noms de fichiers à l\'exception de ".", "@", "/", " ", "_", "-", "é" et "è".';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php