Question

Why does PHP not support relative URLs?

Can this be done with other programming languages? That the the server side can micro quick detect?

$urla="http://cdn.domain.net";
$urlb="//cdn.domain.net";

if(@fopen($urla,"r")){
// I work
}

if(@fopen($urlb,"r")){
// I do not work
}

Now that I mention it, much of the prime PHP cannot work like this or does not support as I am guessing due to server side – perhaps modification of CORE PHP is need in the C libraries? (What is a Relative URL?)

Answer 1

Why does PHP not support relative URLs?

Relative URL support needs a Base URL the relative URL is relative to. Please see 4.2. Relative Reference in RFC 3986 URI Generic Syntax.

Taken that into account, there is a PHP Library available that actually does support relative URLs and it is compatible with fopen. It’s called Net_URL2:

require_once('Net/URL2.php'); # or configure your autoloader

$baseUrl = 'http://cdn.domain.net';

$hrefRelativeOrAbsolute = '//cdn.domain.net';

$baseUrl = new Net_URL2($baseUrl);

$urlAbsolute = (string) $baseUrl->resolve($hrefRelativeOrAbsolute);

See as well problem with adding root path using php domdocument.