PHP 8.1 Never Return Type

PHP 8.1 introduced a new return type called never, primarily used to indicate that a function will never return a value. Understanding and implementing this new feature optimizes your code and clarifies its intent. Let's learn how to use the never return type effectively.

What Is the never Return Type?

The never type explicitly signifies that a declared function will not return any value. Instead, It will either throw an exception or terminate the script execution through a die() or exit() call.

Benefits of Using the never Return Type

Utilizing the never return type comes with several benefits:

• Readability: Instant clarity that the function won't return.
• Type Safety: Reinforces the function's contract.
• Quality: Elevates the robustness of your code.
• Performance: Removes the need to check for return values.

Practical Applications

The never return type is useful in various scenarios:

• Exception-throwing functions: Functions that throw exceptions should use the never return type.
• Endless loops: When a function contains an endless loop, never is the appropriate return type.
• Exit or die statements: Functions that terminate script execution with exit or die should also use never.
• Fatal error handlers: You can use never in custom error handlers that throw exceptions or end execution.
• HTTP response functions: Create helper functions for sending HTTP responses and exiting the script with never.
• Using never with database queries: If a function performs a database query and exits the script if the query fails, use never.

Examples and Usage Scenarios

Here are some examples of how to use the never return type effectively:

// Use-case: Function that throws an exception
function throwError(): never {
    throw new Exception("An error occurred.");
}

// Use-case: Redirects and exits
function redirect(string $uri): never {
    header('Location: ' . $uri);
    exit;
}

// Use-case: Throws a custom exception
function fail(string $message): never {
    throw new InvalidArgumentException($message);
}

// Use-case: Contains an infinite loop
function infiniteLoop(): never {
    while (true) {
        // Infinite loop
    }
}

// Use-case: Terminates the script
function endScript(): never {
    exit;
}

// Use-case: Custom error handler
function customErrorHandler(int $severity, string $message, string $file, int $line): never {
    throw new ErrorException($message, 0, $severity, $file, $line);
}

// Use-case: Sets HTTP 404 status and exits
function send404Error(): never {
    http_response_code(404);
    include '404.php';
    exit;
}

// Use-case: Inserts user into DB and exits on failure
function insertUser(array $userData, PDO $pdo): never {
    $query = 'INSERT INTO users (name, email) VALUES (:name, :email)';
    $stmt = $pdo->prepare($query);
    $stmt->bindParam(':name', $userData['name']);
    $stmt->bindParam(':email', $userData['email']);
    if (!$stmt->execute()) {
        exit('Failed to insert user.');
    }
}

Common Mistakes to Avoid

Here are some common mistakes to avoid when using the never return type:

Mixing Return Values

You can't include other return types or values when using never. The following is incorrect:

// Incorrect Use-case: Mixing with other return types
function incorrectUsage(): never | int {
    // some code
}

Using return Statements

Attempting to return a value in a function marked as never will result in a compile-time error.

// Incorrect Use-case: Using return statements
function doSomething(): never {
    return "This will not compile.";
}

Empty functions

An empty function cannot be marked with the never return type as it implicitly returns null.

// Incorrect Use-case: Empty function
function doNothing(): never {
    // Does nothing
}

Conclusion

The never return type in PHP 8.1 brings improved readability, type safety, and overall code quality. Eliminate ambiguity and enhance the contract between your code and its users by integrating this feature into your projects. Start using never to optimize your PHP code today!