How do I get the final, redirected, canonical URL of a website using PHP?

Question

In the days of link shorteners and Ajax, there can be many links that ultimately point to the same content. I was wondering what the best way is to get the final, best link for

Answer 1

I wrote you a little function to do it. It's simple, but it may be a starting point for you. Note: the http://dlvr.it/xxb0W url returns an invalid URL for it's Location response header.

You'll need the Altumo PHP library for it to work. It's a library that I wrote, but it's MIT license, as is this function.

See: https://github.com/homer6/altumo

Also, you'll have to wrap the function in a try/catch.

/**
* Gets the final URL of a URL that will be redirected.
* 
* @param string $url_string
* @throws \Exception                    //on error
* @return string
*/
function get_final_url( $url_string ){

    while( 1 ){

        //validate URL
            $url = new \Altumo\String\Url( $url_string );

        //get the Location response header of the URL
            $client = new \Altumo\Http\OutgoingHttpRequest( $url_string );
            $response = $client->sendAndGetResponseMessage();
            $location = $response->getHeader( 'Location' );

        //return the URL if no Location header was found, else continue
            if( is_null($location) ){
                return $url_string;
            }else{
                $url_string = $location;
            }

    }

}

echo get_final_url( 'your url here' );

Please let me know if you'd like further modifications or help getting it going.