check if an url is valid

Hi! can you tell me how can I check if a remote files exists? I've tried with fopen, but I've a warning on STDOUT if file doesn't exists. I wouldn't redirect the STDERR to solve this problem. I could use fsockopen, but I feel that this is a bad solution. Can you tell me something that is easy? I would a function that return true/false if an url is/not is valid; without error to browser Thanks