What are common reasons for the header('Location...') function not working in PHP, especially when transitioning from local development to a live server?

One common reason for the header('Location...') function not working when transitioning from local development to a live server is output being sent before the header function is called. To solve this, make sure there is no output (including whitespace) before the header function is called. Another reason could be the use of relative paths in the location parameter, which may not work consistently across different environments. To fix this, use absolute paths or ensure that the paths are correct for the live server.

<?php
ob_start(); // Start output buffering
// Your PHP code here
ob_end_clean(); // Clean the output buffer

// Redirect to a new page
header('Location: https://www.example.com/newpage.php');
exit;
?>