What is the difference between time() and microtime() in PHP and how does it affect file naming?

The main difference between `time()` and `microtime()` in PHP is that `time()` returns the current Unix timestamp (seconds since the Unix Epoch), while `microtime()` returns the current Unix timestamp with microseconds. When using these functions for file naming, `time()` is suitable for creating unique file names based on seconds, while `microtime()` can be used for even more precise file naming based on microseconds.

// Using time() for file naming based on seconds
$file_name = 'file_' . time() . '.txt';

// Using microtime() for file naming based on microseconds
$file_name = 'file_' . str_replace(' ', '', microtime()) . '.txt';