PHP: pseudo-random string of defined length

mehRandomString.php

<?php

function randString($length, $charset = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-0123456789')
{
    $str = '';
    $count = strlen($charset) - 1;
    while ($length--) {
        $str .= $charset[mt_rand(0, $count)];
    }
    return $str;
}