Eric @ EricBess WebHome

<?php
$path_a = 'http://www.php.net/manual/en/install.php';
$path_b = 'http://www.php.net/downloads';
 
echo "\nPath A:  " . $path_a;
echo "\nPath B:  " . $path_b;
echo "\nA to B:  " . findRelativePath($path_a, $path_b); //  ../../downloads/
echo "\nB to A:  " . findRelativePath($path_b, $path_a); //  ../manual/en/install.php
?>

<?php
function findRelativePath($path_1, $path_2)
{
    if ($path_1 == ""  ||  $path_2 == "")
    {
        return false;
    }
 
    preg_match_all("/^(\\/|\w:\\/|https?:\\/\\/[^\\/]+\\/)?(.*)$/i", $path_1, $matches_1, PREG_SET_ORDER);
    preg_match_all("/^(\\/|\w:\\/|https?:\\/\\/[^\\/]+\\/)?(.*)$/i", $path_2, $matches_2, PREG_SET_ORDER);
 
    if ($matches_1[0][1] != $matches_2[0][1])
    {
        return false;
    }
 
    $path_1_parts = explode("/", $matches_1[0][2]);
    $path_2_parts = explode("/", $matches_2[0][2]);
 
    while (isset($path_1_parts[0])  &&  isset($path_2_parts[0]))
    {
        if ($path_1_parts[0] != $path_2_parts[0])
        {
            break;
        }
 
        array_shift($path_1_parts);
        array_shift($path_2_parts);
    }
 
    for ($i = 0, $path = ""; $i < count($path_1_parts)-1; $i++)
    {
        $path .= "../";
    }
    return $path . implode("/", $path_2_parts);
}
?>