PHP 8 introduces a number of important new features that significantly improve performance, code readability and development experience. 1. JIT compilation improves execution speed, especially for CPU-intensive tasks, and is controlled through php.ini configuration; 2. Union types support more flexible type declarations, allowing direct definition of multiple parameter types; 3. Named parameters enhance the readability and security of function calls to avoid order errors; 4. Match expressions provide a more concise condition return method than switch, with strict comparison and non-penetration characteristics; 5. Constructor attribute improvement reduces boilerplate code, making class definition more concise; in addition, it also includes improvements such as throw expressions, attribute replacement annotations, which make PHP 8 more modern, powerful and easy to use overall. Although upgrades require investment, it is worth it.

PHP 8 brought a bunch of notable changes and new features that improve performance, code readability, and developer experience. If you're working with PHP or planning to upgrade, here are the most impactful additions worth knowing.

1. JIT Compilation – Faster Execution

One of the biggest highlights in PHP 8 is the introduction of JIT (Just-In-Time) compilation . This feature compiles parts of PHP code into native machine code at runtime, reducing interpretation overhead.

• It doesn't speed up every script equally — it shines more in CPU-intensive tasks like heavy math operations or large-scale APIs.
• You can control how it works using settings in php.ini , such as opcache.jit_buffer_size and opcache.jit .

Keep in mind: for most web applications, the performance boost might be subtle unless your app does heavy processing.

2. Union Types – More Flexible Type Declarations

Before PHP 8, if you wanted to accept multiple types in a function parameter or property, you had to rely on comments or skip type checking. Now, union types let you specify that directly:

 public function setResponse(string|int|float $value): void {
    // ...
}

This makes type declarations clearer and safer without needing custom logic or loose typing.

Also, PHP 8.1 adds support for never , true , false , and even array | null combinations, giving you fine-grained control over what values ??are allowed.

3. Named Arguments – Cleaner and Safer Function Calls

Named arguments allow you to pass parameters by name instead of position:

 function createPost(string $title, string $content, bool $published = false) { ... }

createPost(title: "Hello World", content: "My first post", published: true);

Why this matters:

• Improves readability, especially when calling functions with many optional parameters.
• Reduces mistakes from passing arguments in the wrong order.
• Works with both built-in and custom functions.

It's especially useful when skipping optional parameters — no need to fill them with null just to reach the one you want to set.

4. Match Expressions – A Smarter Alternative to Switch

Match expressions offer a cleaner way to handle conditional returns. They're similar to switch but more concise and expressive:

 $status = match($code) {
    200 => 'OK',
    404 => 'Not Found',
    500 => 'Server Error',
    default => 'Unknown',
};

Key differences:

• Returns a value directly.
• Uses strict comparison ( === ) by default.
• No fall-through behavior, so no need for break .

They help reduce boilerplate and make logic easier to follow.

5. Constructor Property Promotion – Less Boilerplate

If you're writing classes with a lot of properties initialized via constructors, this change saves time:

 class User {
    public function __construct(
        public string $name,
        public int $age
    ) {}
}

Instead of declaring properties and assigning them separately, you do it all in the constructor signature. Makes object-oriented code much cleaner and easier to maintain.

There are other smaller improvements too — like better error handling with throw expressions, attributes replacing docblock annotations, and stricter type checks across the board.

All these changes together make PHP 8 feel more modern and powerful while staying approachable. Upgrading might take some effort depending on your codebase, but the benefits in clarity, safety, and performance are definitely worth it.

Basically that's it.

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