php convert all links to absolute urls

Question

I am writing a website crawler in php and I already have code that can extract all links from a site. A problem: sites use a combination of absolute and relative urls. Examples (http replaced with hxxp as I can't post hyperlinks):

hxxp://site.com/

site.com

site.com/index.php

hxxp://site.com/hello/index.php

/hello/index.php

hxxp://site2.com/index.php

site2.com/index.php

I have no control over the links (if they are absolute/relative), but I do need to follow them. I need to convert all these links into absolute URLs. How do I do this in php?

Answer 1

Here's a start

// Your crawler was sent to this page.
$url = 'http://example.com/page';

// Example of a relative link of the page above.
$relative = '/hello/index.php';

// Parse the URL the crawler was sent to.
$url = parse_url($url);

if(FALSE === filter_var($relative, FILTER_VALIDATE_URL))
{
    // If the link isn't a valid URL then assume it's relative and
    // construct an absolute URL.
    print $url['scheme'].'://'.$url['host'].'/'.ltrim($relative, '/');
}

Have a look into the http_build_url method as another way of creating an absolute anchor.