php计算两个文件夹的相对路径

<?php 
include ‘../../c/e/one.php‘;
echo "\n";
echo ‘this is two‘;
echo "\n";

$a = "/a/b/c/d/e.php";
$b = "/a/b/12/34/c.php";

$cnta = strlen($a);
$cntb = strlen($b);

$cnt = max($cnta,$cntb);
echo $cnt,"\n";

for($i=1;$i<$cnt;$i++){
    $str_a = substr($a,0,$i);
    $str_b = substr($b,0,$i);
    if($str_a == $str_b){
        $base = $str_a;
    }else{
        break;
    }
}
echo $base,"\n";
$start = strlen($base);
$a_arr = explode(‘/‘,substr($a,$start));
$a_c_cnt = count($a_arr)-1;

$path = ‘‘;
for($i=0;$i<$a_c_cnt;$i++){
    $path .= "../";
}
$path .= substr($a,$start);
echo $path,"\n";

$b_arr = explode(‘/‘,substr($b,$start));
$b_c_cnt = count($b_arr)-1;
$path = ‘‘;
for($i=0;$i<$b_c_cnt;$i++){
    $path .= "../";
}
$path .= substr($b,$start);
echo $path,"\n";