You may use Directory Functions: http://php.net/manual/en/book.dir.php
Simple example from opendir() function description:
<?php
$dir_path = "/path/to/your/dir";
if (is_dir($dir_path)) {
if ($dir_handler = opendir($dir_path)) {
while (($file = readdir($dir_handler)) !== false) {
echo "filename: $file : filetype: " . filetype($dir_path . $file) . "\n";
}
closedir($dir_handler);
}
}
?>