There are many problems with that.
1 - Unless you spacificaly tell it, PHP will wait till the end of the script before sending ANY information to the browser so that script would not be sent till after 3 seconds.
2 - If it was shown then header() would not work as headers need to be sent before any data.
3 - Most browsers (IE, Netscape/firefox etc) only update the display every 100bites or so
Try this
<?php
header("Refresh: 3;URL=movie_registration.php");
echo "Your username and password do not match our records";
?>
This will display the page but tell the browser to refresh after 3 seconds to the new page
Regards,
Sam Rudge