[PHP-DEV] how can I check the url's validity

[jackywdx]

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.