What are common causes of the "headers already sent" error in PHP when working with sessions?

The "headers already sent" error in PHP when working with sessions commonly occurs when there is whitespace or output sent before session_start() is called. To solve this issue, ensure that session_start() is called at the beginning of the script before any output is sent to the browser. 

<?php
// Start the session at the beginning of the script
session_start();

// Your PHP code here
?>

Keywords

output buffering session_start whitespace include header

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