http://it2.php.net/manual/it/ref.filesystem.php

// ---------------------- elenco file dir
$d = dir("tua_directory");
//echo "Handle: ".$d->handle."
\n";
//echo "Path: ".$d->path."
\n";

while ($entry = $d->read()) {
//echo $entry."
\n";
if ((substr($entry,strlen($entry)-7,strlen($entry))) == "chi.chi" ){
unlink($entry);
}
}

$d->close();