How can PHP beginners troubleshoot and resolve the error message "Cannot modify header information - headers already sent"?

The error message "Cannot modify header information - headers already sent" typically occurs when there is whitespace or output sent before the PHP header() function is called. To resolve this issue, make sure there is no output sent to the browser before calling header() function, and ensure that there are no spaces or empty lines before the opening <?php tag in your PHP file. 

&lt;?php
ob_start(); // Start output buffering

// Your PHP code here

ob_end_flush(); // Flush output buffer

Keywords

PHP header output buffering ob_start error message

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