PHP Matching URLs and using preg_replace_callback()

Question

I use the following to find all URL´s inside $content

 $content = preg_match_all( '/(http[s]?:[^\s]*)/i', $content, $links );

But this will depend on the http:// part in http://www.google.com/some/path .

My questions are :

1 - How can I modify it in order to hit also the links that are start with only www , e.g. www.google.com?

2 - The main aim is to find the links, and replace them with a value that is returned from another function. I tried preg_match_callback() , but it is not working (probably using it wrong ..

$content = preg_replace_callback(
           "/(http[s]?:[^\s]*)/i",
            "my_callback",
            $content);

function my_callback(){

// do a lot of stuff independently of preg_replace
// adding to =.output...

return $output;
}

Now , in my logic (which is probably wrong ) all matches from the $content would be replaced by $output. what am I doing wrong ?

(please no anonymous functions - i am testing on an old server)

EDIT I - after comments , trying to clarify with more details

function o99_simple_parse($content){

$content = preg_replace_callback( '/(http[s]?:[^\s]*)/i', 'o99_simple_callback', $content );


return $content;
}

callback :

function o99_simple_callback($url){
    // how to get the URL which is actually the match? and width ??
        $url = esc_url_raw( $link );
        $url_name = parse_url($url); 
        $url_name = $description = $url_name['host'];// get rid of http://..
        $url = 'http://something' .  urlencode($url)   . '?w=' . $width ; 
        return $url; // what i really need to replace 
    }

Answer 1

To modify the regex you already have to allow URLs that begin with www, you'd simply write this:

/((http[s]?:|www[.])[^\s]*)/i
  +         ++++++++