What potential issues can arise when using the header() function in PHP to redirect users?

One potential issue that can arise when using the header() function in PHP to redirect users is the "Cannot modify header information - headers already sent" error. This error occurs when there is any output (such as whitespace or HTML tags) sent to the browser before the header() function is called. To solve this issue, make sure to call the header() function before any output is sent to the browser.

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

// Your PHP code here

header("Location: http://www.example.com"); // Redirect the user

ob_end_flush(); // Flush the output buffer
?>