class A{

    public $b;

    public $f;

    function __construct( B $b , $f = 1 ){

        $this->b = $b;

        $this->f = $f;

    }

}

class B{}

class GenClass{

    public function getObj( $class ,$params = [] ){

        $rel = new ReflectionClass( $class );

        $paramObjs = $rel->getConstructor()->getParameters();

        $parIns = $this->getParIns($paramObjs);

        $ret = $rel->newInstanceArgs($parIns);

        return $ret;

    }

    public function getParIns( $paramObjs ){

        $ret = [];

        foreach ( $paramObjs as $params){

            $dep = $params->getClass();

            if ($params->isDefaultValueAvailable()) {

                $ret[] =  $params->getDefaultValue();

            }else{

                $ret[] = $this->getIns( $params->name );

            }

        }

        return $ret;

    }

    public function getIns( $class, $param = [] ){

        return new $class();

    }

}

$s = (new GenClass())->getObj('A',[]);

var_dump($s);

die();