How can PHP developers ensure that header instructions are placed before any output in their scripts?

To ensure that header instructions are placed before any output in PHP scripts, developers can use the ob_start() function to buffer the output. This function will capture any output generated by the script and prevent it from being sent to the browser until the headers are set. Once the headers are set, developers can use ob_end_flush() to send the buffered output to the browser.

<?php
ob_start();

// Set headers
header('Content-Type: text/html');

// Output content
echo 'Hello, World!';

// Send buffered output to the browser
ob_end_flush();
?>