levenshtein distance (advanced))

/*
* Levenshtein comparison from 0 to 100: 0 being the most similar, 100 being the least (from php.net)
*/
function levenshteinDistance2($str1, $str2) {
    $len1 = mb_strlen($str1);
    $len2 = mb_strlen($str2);

    // strip common prefix
    $i = 0;
    do {
        if(mb_substr($str1, $i, 1) != mb_substr($str2, $i, 1))
            break;
        $i++;
        $len1--;
        $len2--;
    } while($len1 > 0 && $len2 > 0);
    if($i > 0) {
        $str1 = mb_substr($str1, $i);
        $str2 = mb_substr($str2, $i);
    }

    // strip common suffix
    $i = 0;
    do {
        if(mb_substr($str1, $len1-1, 1) != mb_substr($str2, $len2-1, 1))
            break;
        $i++;
        $len1--;
        $len2--;
    } while($len1 > 0 && $len2 > 0);
    if($i > 0) {
        $str1 = mb_substr($str1, 0, $len1);
        $str2 = mb_substr($str2, 0, $len2);
    }

    if ($len1 == 0)
        return $len2;
    if ($len2 == 0)
        return $len1;

    $v0 = range(0, $len1);
    $v1 = array();

    for ($i = 1; $i <= $len2; $i++) {
        $v1[0] = $i;
        $str2j = mb_substr($str2, $i - 1, 1);

        for ($j = 1; $j <= $len1; $j++) {
            $cost = (mb_substr($str1, $j - 1, 1) == $str2j) ? 0 : 1;

            $m_min = $v0[$j] + 1;
            $b = $v1[$j - 1] + 1;
            $c = $v0[$j - 1] + $cost;

            if ($b < $m_min)
                $m_min = $b;
            if ($c < $m_min)
                $m_min = $c;

            $v1[$j] = $m_min;
        }

        $vTmp = $v0;
        $v0 = $v1;
        $v1 = $vTmp;
    }

    return $v0[$len1];
}