Add support for method calls on primitive types in PHP

This extension implements the ability to register a class that handles the
method calls to a certain primitive type (string, array, …). As such it
allows implementing APIs like $str->length().

The main purpose of this repo is to provide a proof of concept implementation
that can be used to design the new APIs. The switch to object syntax for
operations on primitive types is a unique opportunity for PHP to redesign many
of its inconsistent core APIs. This repo provides the means to quickly
prototype and test new APIs as userland code. Once the APIs are figured out
it will be proposed for inclusion into PHP.

Note: The ability to register type handlers from userland is just for
prototyping. It’s not something I would actually want in PHP in the end.

Registering type handlers

Type handlers are registered through register_primitive_type_handler. The
function takes a type name (like “string” or “array”) and a class name. The
class should contain static methods, which receive the primitive type as the
first parameter:

<?php

class StringHandler {
    public static function length($self) {
        return strlen($self);
    }

    public static function startsWith($self, $other) {
        return strpos($self, $other) === 0;
    }
}

register_primitive_type_handler('string', 'StringHandler');

$string = "abc";
var_dump($string->length()); // int(3)
var_dump($string->startsWith("a")); // bool(true)

The valid type names are: null, bool, int, float, string, array
and resource. Not all of those will make sense in practice, but for now they
are all supported.

Implemented APIs

As already pointed out in the introduction the main purpose of this repo is
designing good APIs for the primitive types. The implemented APIs are available
in the handlers/ folder (and are obviously work in progress). In order to
load these APIs just include the handlers/bootstrap.php file.

Installation

The master branch supports PHP version 7.0 to 8.1. The extension is incompatible
with the JIT compiler.

Unix

In order to compile and install the extension run the following commands:

phpize
./configure
make
sudo make install

Windows

Download a prebuilt Windows DLL that matches your PHP version
and move it into the ext/ directory of your PHP installation. Furthermore
you’ll have to add extension=php_scalar_objects.dll to your php.ini.

Testing the extension

The extension comes with a run-tests.php file to run the tests. (To see
examples of the implemented APIs you should also look in the tests.) The
script is run as follows:

php run-tests.php -q -p php

Where php is the path to your PHP executable.

Limitations

This extension has a number of limitations:

• Due to technical limitations, it is not possible to create mutable APIs for primitive
  types. Modifying $self within the methods is not possible (or rather, will have no effect,
  as you’d just be changing a copy).