Transform a camel case string to an underscore string

gistfile1.php

<?php

/**
* Transform a camel case string to an underscore string
*
* @param  string $str
* @return string
*/
public static function camelCaseToUnderscore($str)
{
    return strtolower(preg_replace('/([a-z])([A-Z])/', '$1_$2', $str));
}