Hello, I found this function on the web which permits you to list all the files in a specific directory and its sub-directories.    
function ListFiles($dir) {
   if($dh = opendir($dir)) {
    $files = Array();
    $inner_files = Array();
    while($file = readdir($dh)) {
	    if($file != "." && $file != ".." && $file[0] != '.') {
		    if(is_dir($dir . "/" . $file)) {
			    $inner_files = ListFiles($dir . "/" . $file);
			    if(is_array($inner_files)) $files = array_merge($files, $inner_files);
		    } else {
			    array_push($files, $dir . "/" . $file);
		    }
	    }
    }
    closedir($dh);
    return $files;
   }
}
   And here's how to use it:    
foreach (ListFiles('YOUR-DIRECTORY') as $key=>$file){
   echo $file ."<br />";
}
   I hope it helps.