Question

I need to check whether a css file is available or – if not – load a local fallback file. What’s the fastest way in php?

Answer 1

There is no fastest way. If you need and want to probe a remote file, then that requires a HTTP request. There are multiple options for that, but only with slight performance differences. The actual delay comes from issuing a HTTP transfer.

get_headers() is the simplest option:

 $exists = strstr(current(get_headers($url)), "200");