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[PHP-DEV] 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 ha