How to Cast Objects in PHP

Question

Ive some classes that share some attributes, and i would like to do something like:

$dog = (Dog) $cat;

is it possible or is there any gener

Answer 1

You may think about factories

class XyFactory {
    public function createXyObject ($other) {
        $new = new XyObject($other->someValue);
        // Do other things, that let $new look like $other (except the used class)
        return $new;
    }
}

Otherwise user250120s solution is the only one, which comes close to class casting.

Answer 2

class It {
    public $a = '';

    public function __construct($a) {
        $this->a = $a;
    }
    public function printIt() {
        ;
    }
}

//contains static function to 'convert' instance of parent It to sub-class instance of Thing

class Thing extends it {
    public $b = '';

    public function __construct($a, $b) {
        $this->a = $a;
        $this->b = $b;
    }
    public function printThing() {
        echo $this->a . $this->b;
    }
        //static function housed by target class since trying to create an instance of Thing
    static function thingFromIt(It $it, $b) {
        return new Thing($it->a, $b);
    }
}


//create an instance of It
$it = new It('1');

//create an instance of Thing 
$thing = Thing::thingFromIt($it, '2');


echo 'Class for $it: ' . get_class($it);
echo 'Class for $thing: ' . get_class($thing);

Returns:

Class for $it: It
Class for $thing: Thing

Answer 3

a better aproach:

class Animal
{
    private $_name = null;

    public function __construct($name = null)
    {
        $this->_name = $name;
    }

    /**
     * casts object
     * @param Animal $to
     * @return Animal
     */
    public function cast($to)
    {
        if ($to instanceof Animal) {
            $to->_name = $this->_name;
        } else {
            throw(new Exception('cant cast ' . get_class($this) . ' to ' . get_class($to)));
        return $to;
    }

    public function getName()
    {
        return $this->_name;
    }
}

class Cat extends Animal
{
    private $_preferedKindOfFish = null;

    public function __construct($name = null, $preferedKindOfFish = null)
    {
        parent::__construct($name);
        $this->_preferedKindOfFish = $preferedKindOfFish;
    }

    /**
     * casts object
     * @param Animal $to
     * @return Animal
     */
    public function cast($to)
    {
        parent::cast($to);
        if ($to instanceof Cat) {
            $to->_preferedKindOfFish = $this->_preferedKindOfFish;
        }
        return $to;
    }

    public function getPreferedKindOfFish()
    {
        return $this->_preferedKindOfFish;
    }
}

class Dog extends Animal
{
    private $_preferedKindOfCat = null;

    public function __construct($name = null, $preferedKindOfCat = null)
    {
        parent::__construct($name);
        $this->_preferedKindOfCat = $preferedKindOfCat;
    }

    /**
     * casts object
     * @param Animal $to
     * @return Animal
     */
    public function cast($to)
    {
        parent::cast($to);
        if ($to instanceof Dog) {
            $to->_preferedKindOfCat = $this->_preferedKindOfCat;
        }
        return $to;
    }

    public function getPreferedKindOfCat()
    {
        return $this->_preferedKindOfCat;
    }
}

$dogs = array(
    new Dog('snoopy', 'vegetarian'),
    new Dog('coyote', 'any'),
);

foreach ($dogs as $dog) {
    $cat = $dog->cast(new Cat());
    echo get_class($cat) . ' - ' . $cat->getName() . "\n";
}

Answer 4

You can opt for this example below. Hope it will help.

/** @var ClassName $object */

$object->whateverMethod() // any method defined in the class can be accessed by $object

I know this is not a cast but it can be useful sometimes.

Answer 5

Without using inheritance (as mentioned by author), it seems like you are looking for a solution that can transform one class to another with preassumption of the developer knows and understand the similarity of 2 classes.

There's no existing solution for transforming between objects. What you can try out are:

• get_object_vars() : convert object to array
• Cast to Object: convert array to object

Answer 6

It sounds like what you really want to do is implement an interface.

Your interface will specify the methods that the object can handle and when you pass an object that implements the interface to a method that wants an object that supports the interface, you just type the argument with the name of the interface.