example to match w3p_nnnnn.html or w3p_nnnnn.dir,
match of either html or dir is stored into filematches[2]
if ( preg_match("/^w3p[_](\d+)[.]((html)|(dir))/i",$file,$filematches) )
{
$ID = $filematches[1];
$filetype = $filematches[2];
print "$ID, $filetype\n";
}