<?
$auth = false; // Assume user is not authenticated
if (isset( $PHP_AUTH_USER ) && isset($PHP_AUTH_PW)) {
    $filename = 'passfile.txt';
    $file_contents = file($filename);
    foreach ($file_contents as $line) {
        list($username, $password) = explode(':', $line);
        $username = trim($username);
        $password = trim($password);
        if (($username == "$PHP_AUTH_USER") && ($password == "$PHP_AUTH_PW")) {
            $auth = true;
            break;
        }
    }
}
if (!$auth) {
    header('WWW-Authenticate: Basic realm="Calendar"');
    header('HTTP/1.0 401 Unauthorized');
    die('<p>&nbsp;</p><p><center><h1><font color ="red">Authorization Required.</h1><br>Please close this window to try again.</center></font></P>');
} else {
// do something
}
?>