Differences between is_file and file_exists in php

Is_file only checks whether the file exists;
File_exists checks whether the file exists or whether the directory exists;
Is_dir: determines whether a directory exists;

Check the manual. Although the results of both functions are cached, The is_file speed is N times faster.
Note the following:
If the file exists, is_file is N times faster than file_exists;
If the file does not exist, is_file is slower than file_exists;
The conclusion is that the file_exits function does not affect the speed because the file actually exists, but the is_file function has a greater impact.