$valid_pages = array ('apage.php',
'another.php',
'more.php');
if (!in_array($page, validpages)){
// Abort the script
// You should probably write a log message here too
die("Invalid request");
}

instead of:

$valid_pages = array(
"apage.php" => "",
"another.php" => "",
"more.php" => "");

if (!isset($valid_pages[$page])) {
// Abort the script
// You should probably write a log message here too
die("Invalid request");
}

Yours

Gustavo el Geranie