<?php
 
function calculateRelativePath($a,$b) {
    if (empty($a) || empty($b))
        return;
    $flag = "";
    $split1 = explode("/",$a);
    $split2 = explode("/",$b);
    $diff1 = array_diff_assoc($split1, $split2);
    $count = count($diff1 );
    for($i=0; $i < $count-1; $i++) {
        $flag .= "../";
    } 
    $diff2 = array_diff_assoc($split2, $split1);
    return $flag. implode("/",$diff2);
}
$relative = calculateRelativePath("/a/b/c/d/e.php","/a/b/12/34/c.php");
print_r($relative);

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