camel_underline.php

<?php

/***
 * Helper functions to convert strings:
 *  - from CamelCase to camel_case and;
 *  - from under_score to UnderScore
 *
 * These are very probably not fast (or the fastest version).
 ***/

function camelize($str)
{
    return implode('', explode(' ', ucwords(implode(' ', explode('_', $str)))));
}

function underline($str)
{
    $words = array();
    $split = preg_split('/([A-Z])/', $str, -1, PREG_SPLIT_DELIM_CAPTURE|PREG_SPLIT_NO_EMPTY);
    for ($i = 0; $i < count($split); $i += 2) {
        $words[] = strtolower($split[$i] . $split[$i+1]);
    }
    return implode('_', $words);
}

?>