how can I check the url's validity

hi all: I have a problem, I wonder if there is any good way to check the url's validity. For example, the url: http://diybbs.enet.com.cn/thread-3004314-1-1.html How can I check whether the page exsist, meaning it has content, not 404. My server's php version is PHP4.3.9, quite low, and doesn't have curl extension. I have try fsockopen, fopen. But it's not effective enough, a bit slow. I wonder if there is some functions or some ways to quickly detemine whether the url is valid. Thanks.