preg_replace regex for replacing anchor tag where URL is not sample.com

Question

I have a regex for preg_replace which replace anchor tag where some URL(eg sample.com) exists in href. Now what i need is a regex which will replace all other anchor tags which does not contain some URL(eg sample.com).

Here is my regex:

$rw     =   "Go to hell";
$message    =   "<a href='http://twitter.com'>Twitter</a><br/><a href='http://google.com'>Google</a><br/><a href='http://facebook.com'>Facebook</a>";
$message   =   preg_replace("/<a[^>]*\bhref\s*=\s*'(?:[^']*google.com[^']*|[^][^']*facebook.com[^']*)'>(.*)<\/a>/siU", $rw, $message);

Result is:

Twitter (with link)
Go to hell 
Go to hell 

What i need:

Go to hell
Google (with link)
Facebook (with link)

Answer 1

Change your regex pattern as shown below(using lookahead negative assertion ?! ):

...
$message = preg_replace("/<a[^>]*\bhref\s*=\s*'https?:\/\/(www)?(?!(google\.com|facebook\.com))[^']*'>(.*)<\/a>/siU", $rw, $message);

print_r($message);

The output will be:

Go to hell
Google (with link)
Facebook (with link)