What are common reasons for the "Cannot modify header information" warning in PHP scripts?

The "Cannot modify header information" warning in PHP scripts commonly occurs when there is whitespace or output before the header() function is called. To solve this issue, make sure there is no output sent to the browser before calling header() function, and check for any whitespace or characters outside the PHP tags. 

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

// Your PHP code here

ob_end_clean(); // Clean the output buffer
header("Location: newpage.php"); // Redirect to new page
exit();
?>

Keywords

header information warning PHP scripts modify

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