Have a look at $_SERVER['REQUEST_URI'], i.e.
$actual_link = "http://{$_SERVER['HTTP_HOST']}{$_SERVER['REQUEST_URI']}";
(Note that the double quoted string syntax is perfectly correct)
If you want to support both HTTP and HTTPS, you can use
$actual_link = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") . "://{$_SERVER['HTTP_HOST']}{$_SERVER['REQUEST_URI']}";
Note: using this code has security implications. The client can set HTTP_HOST and REQUEST_URI to any arbitrary value it wants.
Source Stackoverflow.com
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