What steps can be taken to troubleshoot the error message "Cannot modify header information - headers already sent" in PHP code?

The error message "Cannot modify header information - headers already sent" in PHP code typically occurs when there is whitespace or output before the header() function is called. To troubleshoot this issue, check for any whitespace or output before the header() function, ensure that the header() function is called before any output is sent to the browser, and use ob_start() to buffer output if necessary. 

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

// Your PHP code here

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

ob_end_flush(); // Flush output buffer
?>

Keywords

PHP header output buffering ob_start error_reporting

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