Class to increase/decrease PHP's memory_limit by a given amount

memory_limit.php

<?php

class MemoryLimit {
    private $num = 0;

    function inc($num) {
        if (!$num)
            return;

        $this->num += $num;

        $val = trim(ini_get('memory_limit'));
        switch (strtolower($val[strlen($val)-1])) {
        case 'g':
            $val *= 1024;
        case 'm':
            $val *= 1024;
        case 'k':
            $val *= 1024;
        }
        if ($val != -1) {
            $val += $num;
            ini_set('memory_limit', $val);
        }
    }

    function __destruct() {
        $this->inc(-$this->num);
    }
}