for the form part
<form method=post action=index.php>
<input type=text name=searchword>
<input type=hidden name=action value=search>
<input type=submit value=submit>
</form>
for the php part
$action = $GET['action'];
$searchword = $GET['searchword'];
if ($action == "search") {
$result = mysql_query("SELECT count() FROM files WHERE name LIKE '$searchword' ",$db);
$count = mysql_result($result,0);
$result = mysql_query("SELECT FROM files WHERE name LIKE '$searchword' ",$db);
}