There is no SQl-inj, it's just a bug in preg_match() function. and this bug really working! I see it.
I've tried linkhttp://<path_to_forum>/moderate.p … st=5'
and saw that this error notice
Warning: gethostbyaddr(): Address is not a valid IPv4 or IPv6 address in /home/******/public_html/forum/moderate.php on line 53
Try it self. By the way it's not working on localhost(like at home server).