PHP if specific value then continue - php

Question

I have made a form, where that if a value is missing the redirect to error page.
<?php
if (empty($_POST['submit']) && empty($_POST['email']))
{
header('Location: empty.php');
exit;
}
?>
Now, Lets say that i have a password that i need my users to type in to proceed, how do i do that, and if its wrong, then how do i redirect them to empty.php?
My problem is that i dont know how to make a "PHP" tag that redirects if not specific value.

Answer 1

Solution (please, read whole post, as there are security holes..., even black holes in the code ;) ):
<?php
if (isset($_POST['password']) && $_POST['password'] == 'yourpasshere')) {
// Password OK, continue
}
else {
// Password not ok, redirect
header('Location: empty.php');
exit;
}
?>
Few words about solution: if $_POST['password'] is not set, the second condition is even not checked, and it go to else. If the $_POST['password'] is set, second condition check if the password is as you want (read security warnings below). If and only if it is OK, the if passed.
There are few important messages however:
1) Never store password in plain text, anywhere! Read this: http://php.net/manual/en/function.password-hash.php. My example is storing password in plain text, but it is only to sketch the possible solution. Every possible leak of your file gain access to your site.
In that case, my answer sketch the logical part (in which you have a problem) of solution, but NEED TO BE CORRECTED IN SENSE OF SAFETY.
2) Always validate form data (minimal solution is to use http://php.net/manual/en/function.htmlspecialchars.php, but this is not perfect, and it is much more better to use preg_match, or even preg_replace for special characters, to remove them
2*) You can validate email using: var_dump(filter_var('bob#example.com', FILTER_VALIDATE_EMAIL)); (doc: http://php.net/manual/en/function.filter-var.php). This is a great function that will try to validate if entered email is really OK.
3) In your code it will redirect to empty page only if BOTH of the POST values are empty. If You want to redirect if any of them is empty use logical OR (||) not AND (&&).