How can I resolve the "Cannot modify header information - headers already sent" error when using session_start() and setcookie() in PHP?

The "Cannot modify header information - headers already sent" error occurs when PHP tries to send headers, such as those set by session_start() or setcookie(), after output has already been sent to the browser. To resolve this issue, make sure that no output is sent before calling functions that modify headers. 

<?php
ob_start(); // Start output buffering

// Your PHP code here

session_start(); // Start the session

// Set a cookie
setcookie("cookie_name", "cookie_value", time() + 3600);

ob_end_flush(); // End output buffering and send output to the browser
?>

Keywords

session_start setcookie headers already sent resolve error

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