Try this:
$handle=opendir($dir_name);
while ($file = readdir($handle))
$filelst = "$filelst,$file";
closedir($handle);
$filelist = explode(",",$filelst);
sort($filelist);
$number_of_files=count($filelist)-3;
echo "Number of files in this folder: $number_of_files<br>";
dd
