What is the common issue with the "Cannot modify header information" warning in PHP scripts?

The common issue with the "Cannot modify header information" warning in PHP scripts occurs when there is output sent to the browser before calling the header() function to set HTTP headers. To solve this issue, make sure there is no whitespace or output (such as echo statements) before calling header(). 

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

// Your PHP code here

header('Location: newpage.php'); // Set HTTP header

ob_end_flush(); // Flush output buffer
?>

Keywords

header warning PHP scripts output buffering ob_start

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