How can the EVA principle help prevent errors like "headers already sent by" in PHP?

The "headers already sent by" error in PHP occurs when output is sent to the browser before headers are set, which can be caused by whitespace or HTML content before the `header()` function is called. To prevent this error, the EVA principle (Echo, Validate, Action) can be followed by ensuring that headers are set before any output is sent to the browser. 

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

// Set headers before any output
header('Content-Type: text/html');

// Output validation or action
echo "Hello, World!";

ob_end_flush(); // Flush the output buffer
?>

Keywords

EVA principle errors headers PHP prevention

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