What is the EVA principle in PHP and how does it relate to handling output before redirection?

The EVA principle in PHP stands for Escape, Validate, and Avoid. This principle is used to ensure that user input is properly handled before being outputted or redirected to prevent security vulnerabilities such as cross-site scripting (XSS) attacks. By escaping user input, validating it against expected formats, and avoiding direct output or redirection, developers can significantly reduce the risk of security breaches. 

// Example of implementing the EVA principle in PHP before redirection

// Escape user input
$username = htmlspecialchars($_POST['username']);

// Validate user input
if (!empty($username)) {
    // Redirect to a new page
    header("Location: welcome.php");
    exit();
} else {
    echo "Invalid username";
}

Keywords

EVA principle PHP output handling redirection error handling

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