$re = '/(\/blog\/post\?id=)([\w\d]*)&(?:\w*.*)(&id\d)(=\d)/m';
$str = '/blog/post?id=34331824c1866ffb&extraParam=23232&id2=2
/blog/post?id=343fb434343&extraParam=XXXX&id2=2
/blog/post?id=34331824c1866ffb&id2=2
/blog/post?id=343fb434343&id2=2';
preg_match_all($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