- preg_replace: documentation ( source)
<?php
$a = 'ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜaaaaaÝÞßàáâãäåæçèéêëìíîïðñòóôõöøùúûýýþÿ';
$b = 'aaaaaaaceeeeiiiidnoooooouuuuybsaaaaaaaceeeeiiiidnoooooouuuyyby';
preg_replace('/[^a-zA-Z0-9_ %\[\]\.\(\)%&-]/s', '', $a);
echo $a;