What are common reasons for the "Cannot send session cookie" error in PHP when using the session_start() function?

The "Cannot send session cookie" error in PHP when using the session_start() function commonly occurs when output has been sent to the browser before starting a session. To solve this issue, make sure that session_start() is called before any output is sent to the browser, such as HTML, whitespace, or error messages.

<?php
// Start the session before any output is sent
session_start();

// Your PHP code here
?>