How can PHP developers avoid the "headers already sent" error when working with file uploads?

When working with file uploads in PHP, developers can avoid the "headers already sent" error by ensuring that no output is sent to the browser before calling the header() function. This error typically occurs when there is whitespace or other characters sent before the header function is called, causing PHP to be unable to modify the HTTP headers. 

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

// Process file upload here

ob_end_clean();
// Clean (erase) the output buffer and turn off output buffering

// Now headers can be sent without any issues
header('Location: success.php');
?>

Keywords

file uploads headers already sent ob_start ob_clean output buffering

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