PHP scandir()

scandir() function scans the whole directory and list all files and subdirectories. It returns an array of all filenames, or FALSE if failed.
   array scandir(str dir [, int order = SCANDIR_SORT_ASCENDING, resource context]);

<?PHP
	$dir = "/usr/";
	foreach (scandir($dir) as $f) 
	{
	  if ($f !== '.' and $f !== '..')
	  {
		  echo "$f\n";
	  }
	}
?>

There are three sorting parameters:
   SCANDIR_SORT_ASCENDING,
   SCANDIR_SORT_DESCENDING,
   SCANDIR_SORT_NONE.

To get all files in a directory with certain pattern, use glob() function:

<?PHP
    $dir = "/usr/";
	$arrfiles = glob('*.txt');
	var_dump($arrfiles);
?>

The following code can list all files in a specified directory.

<?PHP
	function allfiles($dir, $prefix = '')
	{
		$dir = rtrim($dir, '\\/');
		$result = array();
		foreach (scandir($dir) as $f) {
		  if ($f !== '.' and $f !== '..') {
			if (is_dir("$dir\\$f")) {
			  $result = array_merge($result, allfiles("$dir\\$f", "$prefix$f\\"));
			} else {
			  $result[] = $prefix.$f;
			}
		  }
		}
		return $result;
	}
?>

By default, all the files returned by scandir() will be sorted ascending. Following code can sort all the files by the date modified.

<?PHP
	function allfiles($dir, $prefix = ''){...}  //See above

	$dir = "used/";
	$files = allfiles($dir);
	$times = array();
	foreach ($files as $file)
	{
		$times[$file] = filemtime($dir.$file);
	}
	arsort($times); //from most recently modified to ...
	//asort($times); //reverse
	$files = array_keys($times);
?>

Following code can sort all the files by file size.

<?PHP
	function allfiles($dir, $prefix = ''){...}  //See above

	$dir = "used_files/";
	$files = allfiles($dir);
	$arrsizes = array();
	foreach ($files as $file)
	{
		$arrsizes[$file] = filesize($dir.$file);
	}
	arsort($arrsizes, SORT_NUMERIC); //from largest size to smallest size
	//asort($arrsizes, , SORT_NUMERIC); //reverse
	$files = array_keys($arrsizes);
?>