xphp

What it is

xphp is a superset of php that gives developers real generics, powered by monomorphization at compile time.

In a more inspirational mood, it is a fast lane for the php language, a bridge between what developers need today and what php will support in the future.

How it works

Generics specialize into concrete classes with native typehints the engine enforces, so the safety is real and the abstraction compiles away to nothing.

The compiler turns xphp into regular php. In the end it's good old modern php, but developers and AI agents have richer abstractions to design better solutions.

Ecosystem and community first

The single biggest asset of any programming language is the community and ecosystem around it, much more than its syntax and features.

We believe that meeting a community where it is, respecting their culture, history and work compounds far better than asking them to leave all of that behind.

The design choice to compile to vanilla php is a deliberate commitment to contribute to the php community and its ecosystem.

Principles

Whenever we make an architectural decision, it must be supported by the following non-negotiable principles:

1. Zero Runtime Penalty

Abstractions should not cost performance. By relying on monomorphization rather than runtime reflection hacks, the output is plain php classes. opcache likes that, and execution speed remains identical to handwritten, optimized php code.

2. Maximum Runtime Safety

xphp bakes the types directly into the generated php code. If a boundary is crossed or a third-party plain php library misuses your code, it triggers a native php error. The runtime never lies.

3. Progressive Enhancement

It must play nicely with normal php codebases. A team should be able to write a single xphp file in a php application, compile it, and use it seamlessly.

No custom runtimes, no HHVM style ecosystem splits.

4. Developer Experience

The tooling must be fast and native as in every modern ecosystem. IDEs should be able to read xphp files, while the php runtime happily consumes the compiled php files.

Generics: the start, not the finish line

Adding native generics to php -- a long-awaited php feature -- is genuinely hard work.

The object model that's served the ecosystem for two decades doesn't bend easily.

Supporting generics proves that the compile-to-vanilla model handles non-trivial type-system additions. The remaining features are on the roadmap: type aliases, literal types, mapped and conditional types to name a few.

Getting started

1. Install the xphp package

composer require --dev xphp-lang/xphp

2. Enhance your PSR-4 autoload config

Add a PSR-4 entry to composer.json so the standard autoloader finds the specialized classes without manual require.

{
  "autoload": {
    "psr-4": {
      // generics will be converted into specialized classes,
      // they need to have their own namespace.
      "XPHP\\Generated\\": "<cache>/Generated/",
      "App\\": [
        // path to your normal/regular php code
        "<source>",
        // some `xphp` files just need to be rewritten into native php to use specialized classes,
        // but their namespace will remain the same.
        "<target>"
      ],
    }
  }
}

After that, update your autoload file via composer dump-autoload.

3. Write xphp code

You can define a generic class and instantiate it exactly as you would expect:

// <source>/Collection.xphp
namespace App;

class Collection<T> {
    private T[] $items;

    // The generic 'T' is used directly in the constructor signature
    public function __construct(T ...$items) {
        $this->items = $items;
    }

    public function first(): ?T {
        return $this->items[0] ?? null;
    }
}

// <source>/main.xphp
namespace App;

$users = new Collection<User>(
    new User('Alice'),
    new User('Bob')
);

4. Compile

vendor/bin/xphp compile <source> <target> <cache>

Argument	Purpose
<source>	Directory of .xphp files (PSR-4 layout)
<target>	Where rewritten .php files land -- your user code with generic call sites replaced
<cache>	Where specialized classes live

p.s. you can gitignore files in <target> and <cache> as they can be generated in your CI/CD pipeline.

Sample output

// <cache>/Generated/Collection_User.php
namespace XPHP\Generated;

use App\User;

// p.s. in reality it uses a hash in the class name,
// but developers won't touch that,
// only php runtime will see the hashed names.
class Collection_User {
    private array $items;

    // The generic 'T' is replaced natively with the concrete 'User' type
    public function __construct(User ...$items) {
        $this->items = $items;
    }

    public function first(): ?User {
        return $this->items[0] ?? null;
    }
}

// <target>/main.php
namespace App;

use XPHP\Generated\Collection_User;

// The generic instantiation is mapped directly to the generated class
$users = new Collection_User(
    new User('Alice'),
    new User('Bob')
);

5. Deploy

The compiler monomorphizes the generic classes and converts downstream code into native php code.

Meaning every place where generics are declared or used is converted into normal php code. No impact on the runtime. You still deploy php code.

Project structure

<root>/
├── <source>         # php/xphp source files (PSR-4: namespace mirrors directory structure)
├── <target>         # rewritten .php (gitignored, generated)
├── <cache>          # specialized classes (gitignored, generated)
└── composer.json    # PSR-4: XPHP\Generated\ => <cache>/Generated/

See also

• Type-system comparison
• Full generics reference