What are some common pitfalls to avoid when implementing user input forms in PHP?

Common pitfalls to avoid when implementing user input forms in PHP include not sanitizing user input to prevent SQL injection attacks, not validating input to ensure it meets expected criteria, and not properly escaping output to prevent cross-site scripting attacks. 

// Sanitize user input to prevent SQL injection
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);

// Validate input to ensure it meets expected criteria
if (!filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
    // handle invalid email input
}

// Escape output to prevent cross-site scripting
echo htmlspecialchars($_POST['comment']);

Keywords

SQL injection Cross-site scripting (XSS) Form validation Sanitization Input filtering

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