PHP ２つの文字列の距離を調べるレーベンシュタイン距離 levenshtein()

<?php
function test_levenshtein($str1, $str2)
{
	$r = levenshtein($str1, $str2);
	echo "[$str1] [$str2] = $r\n";
}

test_levenshtein("hoge","hoge");
test_levenshtein("hoge","hage");
test_levenshtein("hoge","hoge2");
test_levenshtein("1hoge","hoge");
test_levenshtein("oldpasswd","newpasswd");
test_levenshtein("hoge23","hoge45");
test_levenshtein("google.com","google.co.jp");
test_levenshtein("yahoo.com","google.com");
?>

[hoge] [hoge] = 0
[hoge] [hage] = 1
[hoge] [hoge2] = 1
[1hoge] [hoge] = 1
[oldpasswd] [newpasswd] = 3
[hoge23] [hoge45] = 2
[google.com] [google.co.jp] = 3
[yahoo.com] [google.com] = 6