Unique and temporary file names in PHP?

I’ve used uniqid() in the past to generate a unique filename, but not actually create the file.

$filename = uniqid(rand(), true) . '.pdf';

The first parameter can be anything you want, but I used rand() here to make it even a bit more random. Using a set prefix, you could further avoid collisions with other temp files in the system.

$filename = uniqid('MyApp', true) . '.pdf';

From there, you just create the file. If all else fails, put it in a while loop and keep generating it until you get one that works.

while (true) {
 $filename = uniqid('MyApp', true) . '.pdf';
 if (!file_exists(sys_get_temp_dir() . $filename)) break;
}