Question

I have one class that creates an instance of another class. Is it possible for the second class to retrieve parameters from the calling class.

For example

Class_A {
    protected $myArray = array('item 1', 'item2', 'item3')

    public function __construct()
    {
        $nextClass = new ClassB();
        echo $nextClass->countArrayItems();
    }
}

Class_B {
    public function countArrayItems()
    {
        return count(Class_A->myArray);
    }
}

$newClass = new Class_A;

Answer 1

You could pass a reference to your Class_A instance to your Class_B constructor:

Class_A {
    public $myArray = array('item 1', 'item2', 'item3')

    public function __construct()
    {
        $nextClass = new Class_B($this);
        echo $nextClass->countArrayItems();
    }
}

Class_B {
    public function __construct($classA_instance) {
        $this->classA_instance = $classA_instance;
    }
    public function countArrayItems()
    {
        return count($this->classA_instance->myArray);
    }
}

$newClass = new Class_A;

(as noted by @chris, Class_A->myArray needs to be public)