When displaying images on our website, we check if the file exists with a call to file_exists(). We fall back to a dummy image if the file was missing.
However, profiling has shown that this is the slowest part of generating our pages with file_exists() taking up to 1/2 ms per file. We are only testing 40 or so files, but this still pushes 20ms onto the page load time.
Can anyone suggest a way of making this go faster? Is there a better way of testing if the file is present? If I build a cache of some kind, how should I keep it in sync.
file_exists() should be a very inexpensive operation. Note too that file_exists builds its own cache to help with performance.