重写字符串中的多个链接URL

Question

I have a long string that contains multiple HTML links that looks like this:

<a href="example.com">My Link></a>

or

<a href="http://example2.com">A different Link</a>

etc.

I need to rewrite these links in PHP so that they send the traffic thru my redirector, so I can tell users they are now leaving to an external domain, etc. My redirector is located at mydomain.com/leaving.php. What I want to do is rewrite these links to something like this:

<a href="http://www.mydomain.com/leaving.php/[URL ENCODED LINK FROM ABOVE]">My Link>

Since not all urls have http:// to begin with I think I need to first strip those from all href links.

How can I grep the correct HTML links (ignoring image src) and url_encode them, and place them back in the original string.

EDIT: Just to clearify, I am not looking for help with the redirection part, just how to replace several URLs within a large string when they sometimes have http

Answer 1

This is just a pseudo that you can modify it as you need.

You need first a .htaccess file that contents following lines;

RewriteEngine On
RewriteRule ^leaving/(.*)$ leaving.php?url=$1 [L]

And in leaving.php;

$url = trim(urldecode($_GET['url']));
// check url is exists
if ($url == '') {
    header('Location: http://www.mydomain.com/');
    exit;
}
// add http if needs
if (substr($url, 0, 7) != 'http://') {
    $url = 'http://'. $url;
}

// send it to target
header('Location: '. $url);
exit;

UPDATE:

If you trying this on server-side, it's useless, cos if PHP sent output once, then u cannot use preg's anymore. So, if want to do this on client-side, following code or somthing like will help you.

var links = document.getElementsByTagName("a"),
    link, href, i = 0;
while (link = links[i++]) {
    // get real url applying getAttribute with "2" params
    if ((href = link.getAttribute("href", 2)) !== null
            // skip non-href links
            && href.charAt(0) !== "#") {
        // add http if not exists
        if (href.substring(0, 7) !== 'http://') {
            href = "http://"+ href
        }
        link.href = "http://www.mydomain.com/leaving/"+ href;
    }
}