How to calculate the relative path between two files in PHP

For example:

The path to file A is/home/web/lib/img/cache.php

The path to file B is/home/web/api/img/show.php

So, the path to file a relative to File B is ... /.. /lib/img/cache.php, that is, file B accesses the relative path of file a.

function Getrelativepath

<?php  
/** calculates the path1 relative to path2 path, that is, the relative path of path2 reference paht1 
* @param  string $path 1 
* @param  string $ path2 
* @return String
/function Getrelativepath ($path 1, $path 2) {  
    $arr 1 = explode ('/', $path 1);  
    $arr 2 = explode ('/', $path 2);  
      
    Gets part of the same path  
    $intersection = Array_intersect_assoc ($arr 1, $arr 2);  
      
    $depth = 0;  
      
    For ($i =0, $len =count ($intersection); $i < $len; $i + +) {  
        if (!isset ($intersection [$i])) {  
            $depth = $i;  
            break;  
        }  
    }  
      
    To path2 the/into. /,path1 gets the back part and then  
    $tmp = Array_merge (Array_fill (0, Count ($arr 2)-$depth-1, ' ... '), Array_slice ($arr 1, $depth));  
      
    $relativePath = implode ('/', $tmp);  
      
    return $relativePath;  
>

Demo

<?php  
$path 1 = '/home/web/lib/img/cache.php ';  
$path 2 = '/home/web/api/img/show.php ';  
      
Echo Getrelativepath ($path 1, $path 2); // .. /.. /lib/img/cache.php  
?>

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