$re = '/http:\/\/mywebsite\.com\/((?:http:\/\/)?[0-9A-Za-z]+(?:-+[0-9A-Za-z]+)*(?:\.[0-9A-Za-z]+(?:-+[0-9A-Za-z]+)*)+(?:\/.*)?)/';
$str = 'http://mywebsite.com/google.com/search=xyz
http://mywebsite.com/yahoo.org/search=xyz
http://mywebsite.com/www.yahoo.org/search=xyz
http://mywebsite.com/msn.co.uk
http://mywebsite.com/http://msn.co.uk
http://mywebsite.com/badname/
http://mywebsite.com/test.com/ww
http://mywebsite.com/-badname.com
http://mywebsite.com/tes-t.com/ww';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php