How can the "headers already sent" error be resolved when using the header() function?

When using the header() function in PHP, the "headers already sent" error occurs when there is output (such as whitespace or HTML) sent before calling the header() function. To resolve this issue, ensure that there is no output sent before calling header() and that the function is called before any output is generated on the page.

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

// Your PHP code here

header("Location: https://www.example.com"); // Example of using header function

ob_end_flush(); // Flush output buffer
?>