Question

I would like for users to be able to enter their company website URL in their company setup dialog, but I need to validate that. Apart from the typical sanitization functions, I would like to check if the URL scheme is http:// or https:// without the assumption the user has already entered it.

My function already parses the entered url to detect the scheme with a regex, but I would like to (ideally) check the URL from the server ala file_get_contents or parse_url and get the scheme, but I don’t know how could I do it.

Answer 1

Take a look at parse_url(). The scheme will be returned in the scheme element of the array.

Edit 1

Partial URLs are also accepted, parse_url() tries its best to parse them correctly.

If the scheme is not present in the URL, then the scheme element will be missing.

Edit 2

As @BenediktOlek says, you can use cURL to query the server:

$curl = curl_init();
curl_setopt_array(
    $curl,
    array(
        CURLOPT_URL            => 'http://www.example.com/',
        CURLOPT_HEADER         => TRUE,  // Output the response headers
        CURLOPT_RETURNTRANSFER => TRUE,  // Return output as a string
        CURLOPT_NOBODY         => TRUE   // Use request method "HEAD"
    )
);
$curlData = curl_exec($curl);
curl_close($curl);

If the server requires an HTTPS connection, and is correctly configured, then it should return a Location: header with an HTTPS URL.