access-interceptor-scope-localizer.md

Access Interceptor Scope Localizer Proxy

An access interceptor scope localizer is a smart reference proxy that allows you to dynamically define logic to be executed before or after any of the proxied object methods' logic.

It works exactly like the access interceptor value holder, with some minor differences in behaviour.

The working concept of an access interceptor scope localizer is to localize scope of a proxied object:

class Example
{
    protected $foo;
    protected $bar;
    protected $baz;

    public function doFoo()
    {
        // ...
    }
}

class ExampleProxy extends Example
{
    public function __construct(Example $example)
    {
        $this->foo = & $example->foo;
        $this->bar = & $example->bar;
        $this->baz = & $example->baz;
    }

    public function doFoo()
    {
        return parent::doFoo();
    }
}

This allows creating a mirror copy of the real instance, where any change in the proxy or the real instance is reflected in both objects.

The main advantage of this approach is that the proxy is now safe against fluent interfaces, which would break an access interceptor value holder instead.

Differences with access interceptor value holder:

• It does NOT implement the ProxyManager\Proxy\ValueHolderInterface, since the proxy itself does not keep a reference to the original object being proxied
• In all interceptor methods (see access interceptor value holder), the $instance passed in is the proxy itself. There is no way to gather a reference to the original object right now, and that is mainly to protect from misuse.

Known limitations

• It is NOT possible to intercept access to public properties
• It is NOT possible to proxy interfaces, since this proxy relies on parent::method() calls. Interfaces don't provide a parent method implementation.
• calling unset on a property of an access interceptor scope localizer (or the real instance) will cause the two objects to be un-synchronized, with possible unexpected behaviour.
• serializing or un-serializing an access interceptor scope localizer (or the real instance) will not cause the real instance (or the proxy) to be serialized or un-serialized
• methods using func_get_args(), func_get_arg() and func_num_arg() will not function properly for parameters that are not part of the proxied object interface: use variadic arguments instead.

Example

Here's an example of how you can create and use an access interceptor scope localizer:

<?php

use ProxyManager\Factory\AccessInterceptorScopeLocalizerFactory as Factory;

require_once __DIR__ . '/vendor/autoload.php';

class Foo
{
    public function doFoo()
    {
        echo "Foo!\n";
    }
}

$factory = new Factory();

$proxy = $factory->createProxy(
    new Foo(),
    ['doFoo' => function () { echo "PreFoo!\n"; }],
    ['doFoo' => function () { echo "PostFoo!\n"; }]
);

$proxy->doFoo();

This sends something like following to your output:

PreFoo!
Foo!
PostFoo!

This is similar logic to what you can find in access interceptor value holder.