What is the significance of the error "header already sent by" in PHP scripts?

The error "header already sent by" in PHP scripts occurs when there is output (such as HTML, whitespace, or error messages) sent to the browser before the header function is called. To solve this issue, make sure that there is no output sent to the browser before calling the header function. This can be done by ensuring that there is no whitespace before the opening <?php tag and that there are no echo or print statements before calling the header function. 

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

// Your PHP code here

ob_end_flush(); // Flush output buffer

Keywords

header output buffering ob_start ob_end_flush PHP scripts

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