Create a string useable as a id or class by removing spaces or special caracters

clean-attribute-id.php

<?php
function clean($string) {
   $string = str_replace(' ', '-', $string); // Replaces all spaces with hyphens.
   $string = preg_replace('/[^A-Za-z0-9\-]/', '', $string); // Removes special chars.
   return strtolower($string);
}

// USE 
echo clean('This is going to be cleaned!'); // Result this-is-going-to-be-cleaned