Get construction parameter dependency from php construction function

Question

Using the php ReflectionClass I can find which parameters I have to inject in a class constructor to create a new instance.

$class = new ReflectionClass($this->someClass);
$constructor = $class->getConstructor();
$parameters = $constructor->getParameters();

Is there also a way to get the dependencies of those parameters. So if the constructor of someClass looks like this:

public function __construct(Dependency $dependency){
    $this->dependency = $dependency;
}

Can I somehow get the class Dependency from the constructor function?

Answer 1

ReflectionMethod::getParameters returns an array of ReflectionParameter objects. ReflectionParameters have an method called getClass that will return information about the typehint of the param.

Example:

<?php
interface Y { }

class X
{
    public function __construct(Y $x, $y=null)
    {

    }
}

$ref = new \ReflectionClass('X');

$c = $ref->getConstructor();
foreach ($c->getParameters() as $p) {
    var_dump($p->getClass());
}

Outputs:

class ReflectionClass#5 (1) {
  public $name =>
  string(1) "Y"
}
NULL

Silex's ControllerResolver has a really nice example of how you might use this:

<?php
// $params is an array of ReflectionParameter instances
protected function doGetArguments(Request $request, $controller, array $parameters)
{
    foreach ($parameters as $param) {
        // check to see if there's a class and if there is, see if the app property
        // is the same type. If so, set the attribute on the request
        if ($param->getClass() && $param->getClass()->isInstance($this->app)) {
            $request->attributes->set($param->getName(), $this->app);

            break;
        }
    }

    return parent::doGetArguments($request, $controller, $parameters);
}