Get url path to url links (PHP)

For get img url I use this on main sites

<a href="./index.html"><img src="./images/logo.png" class="" alt=""></a>

But for sub sites I need to use this

<a href="../index.html"><img src="../images/logo.png" class="" alt=""></a>

How I can get url site using PHP code for this because I would like to create two PHP files, header and footer and I need something like get url site for url links and should work on both sites (main and sub).

I was trying to use

<img src="<?php echo url('images/logo.png') ?>" alt="">

but image not show.

Thanks

If your domain is www.example.com you might want to try getting the required information from the REQUEST_URI that is $_SERVER['REQUEST_URI']

For example:

function get_image_path($image) {

    $parts = explode('/',$_SERVER['REQUEST_URI']);
    $temp = array_shift($parts);
    $image_path = '';
    foreach($parts as $part){
        $image_path.='../';
    }
    return $image_path.$image;
}

Usage:

print get_image_path('images/1.jpg');

This should work for www.example.com/script.php and www.example.com/sub/script.php (and for any number of subfolders nested or not)

Use the same logic for your url($file) function