str_replace function with limit

gistfile1.php

<?php

/**
 * Function for performing replaces on strings that allows for the specification of a limit
 * on the number of occurrences of $search to replace.
 *
 * @see http://www.php.net/manual/en/function.str-replace.php#108239
 *
 * @param $search
 * @param $replace
 * @param $subject
 * @param $limit
 * @param null $count
 * @return mixed
 */
function str_replace_limit($search, $replace, $subject, $limit, &$count = null) {
        $count = 0;
        if ($limit <= 0) return $subject;
        $occurrences = substr_count($subject, $search);
        if ($occurrences === 0) return $subject;
        else if ($occurrences <= $limit) return str_replace($search, $replace, $subject, $count);
        //Do limited replace
        $position = 0;
        //Iterate through occurrences until we get to the last occurrence of $search we're going to replace
        for ($i = 0; $i < $limit; $i++)
                $position = strpos($subject, $search, $position) + strlen($search);
        $substring = substr($subject, 0, $position + 1);
        $substring = str_replace($search, $replace, $substring, $count);
        return substr_replace($subject, $substring, 0, $position + 1);
}


/**
 * Limit counting backwards.
 *
 * @param $search
 * @param $replace
 * @param $subject
 * @param $limit
 * @param null $count
 * @return string
 */
function str_replace_limit_reverse($search, $replace, $subject, $limit, &$count = null) {
        $count = 0;
        $search = strrev($search);
        $replace = strrev($replace);
        $subject = strrev($subject);
        return strrev(str_replace_limit($search, $replace, $subject, $limit, $count));
}

Thanks ;-)

But why not one single function with reverse activated with a negative $limit? (ex. -1 instead of 1)