PHP面试题：如何算出两个文件的相对路径

写一个函数，算出两个文件的相对路径,如:

1. $a = ‘/a/b/c/d/e.php’;
2. $b =’/a/b/12/34/c.php’;

<?php$a = '/a/b/c/d/e.php'; 　　$b ='/a/b/12/34/c.php';$path1 = explode('/',dirname($a));$path2 = explode('/',dirname($b));$aLen = count($path1);$bLen = count($path2);$maxLen = max($aLen,$bLen);for($i = 1; $i < $maxLen; $i++){if($path1[$i] != $path2[$i] && isset($path1[$i])){    if(isset($path2[$i]))$bUrl[]=$path2[$i];    $path .= "../";}else{    $bUrl[]=$path2[$i];}}echo $path.implode('/',$bUrl).'/'.basename($b);?>