What are the key considerations for securely handling user input in PHP forms?

Key considerations for securely handling user input in PHP forms include validating input data to ensure it meets expected criteria, sanitizing input to prevent SQL injection attacks, and escaping output to prevent XSS attacks. It is also important to use prepared statements when interacting with a database to prevent SQL injection vulnerabilities. 

// Validate input data
$username = $_POST['username'];
if (empty($username)) {
    // Handle error
}

// Sanitize input to prevent SQL injection
$username = mysqli_real_escape_string($conn, $username);

// Escape output to prevent XSS attacks
echo htmlspecialchars($username);

// Use prepared statements to interact with the database
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);
$stmt->execute();
$result = $stmt->get_result();

Keywords

SQL injection cross-site scripting htmlspecialchars filter_var prepared statements

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