Aspect Stub

aspect_stub.php

<?php

class Wallet {
    protected $balance;
    public function __construct($initial=0.0) {
        $this->balance = $initial;
    }
    public function add($money) {
        $this->balance += $money;
    }
    public function getBalance() {
        return $this->balance;
    }
}

##############################################################################

class Invocation {
    public $instance;
    public $method;
    public $args;
    public function __construct($instance, \ReflectionMethod $method, array $args) {
        $this->instance = $instance;
        $this->method = $method;
        $this->args = $args;
    }
    public function getParam($index) {
        return $this->args[$index];
    }
    public function proceed() {
        return $this->method->invokeArgs($this->instance, $this->args);
    }
}

interface Pointcut {
    function matchesClass(\ReflectionClass $class);
    function matchesMethod(\ReflectionMethod $method);
}

interface Advice {
    function before(Invocation $invocation);
    function after(Invocation $invocation);
}

interface Aspect {
    function getPointcut();
    function getAdvice();
}

##############################################################################

class WalletPointcut implements Pointcut {
    public function matchesClass(\ReflectionClass $class) {
        return $class->getName() === 'Wallet';
    }
    public function matchesMethod(\ReflectionMethod $method) {
        return $method->getName() === 'add';
    }
}

class WalletAdvice implements Advice {
    public function before(Invocation $invocation) {
        echo 'ADD ' . $invocation->getParam(0) .
             ' to ' . $invocation->instance->getBalance() . PHP_EOL;
    }
    public function after(Invocation $invocation) {}
}

class WalletAspect implements Aspect {
    public function getPointcut() {
        return new WalletPointcut();
    }
    public function getAdvice() {
        return new WalletAdvice();
    }
}

##############################################################################

class Mock {
    public $target;
    public function __construct($target) {
        $this->target = $target;
    }
}

class Stub {
    public $refl;
    public function __construct($target) {
        $this->refl = new \ReflectionClass($target);
        $this->obj = $this->refl->newInstanceArgs(array_slice(func_get_args(), 1));
    }
    public function __call($name, $args) {
        return $this->refl->getMethod($name)->invokeArgs($this->obj, $args);
    }
}

class AspectStub extends Stub {
    public $aspects = array();
    public function addAspect(Aspect $aspect) {
        if ($aspect->getPointcut()->matchesClass($this->refl)) {
            $this->aspects[] = $aspect;
        }
    }
    public function __call($name, $args) {
        $method = $this->refl->getMethod($name);
        foreach ($this->aspects as $aspect) {
            if ($aspect->getPointcut()->matchesMethod($method)) {
                $advice = $aspect->getAdvice();
                $invocation = new Invocation($this->obj, $method, $args);
                $advice->before($invocation);
                $return = $invocation->proceed();
                $advice->after($invocation);
                return $return;
            }
        }
        return $method->invokeArgs($this->obj, $args);
    }
}

##############################################################################

$w = new AspectStub('Wallet', 0.33); // new Wallet(0.33);
$w->addAspect(new WalletAspect());
$w->add(1.66);
print($w->getBalance() . PHP_EOL);