PHP page is delivering the same result regardless of IF condition

Question

I am trying to view a PHP page with and without using an iframe, but the result is the same regardless of the IF condition using $_SERVER['HTTP_SEC_FETCH_DEST'] to detect that it is in an iframe.

if (isset($_SERVER['HTTP_SEC_FETCH_DEST']) and $_SERVER['HTTP_SEC_FETCH_DEST'] == 'iframe') {
// do something
}

The result is always true until I manually refresh the page that isn't using the iframe. Any suggestions to make this work? Seems like some kind of buffer issue, but I have not been able to solve it with flush().

question from:https://stackoverflow.com/questions/65829518/php-page-is-delivering-the-same-result-regardless-of-if-condition

Answer 1

Adding a header to revalidate solved my problem.

header('Cache-Control: no-store, no-cache, must-revalidate');