PHP Get Oldest File

I was looking around to make sure there wasn't some sort of built-in function in PHP now for determining the oldest file in a directory. I didn't find a built-in function that returns the oldest file, but I found plenty of user functions that were not what I was looking for.

So, I wrote my own old file getter function. The function will accept either an array of file paths or a string which will be passed to glob in order to get an array of file paths. The function returns the oldest file found.

function oldest_file($dir)
{
 if(is_string($dir))
 {
  $dir = glob($dir);
 }
 $oldest = array_shift($dir);
 foreach($dir as $file)
 {
  if(filemtime($file) < filemtime($oldest))
  {
   $oldest = $file;
  }
 }
 return $oldest;
}