How to Cast Objects in PHP

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 generic work around?

Its not a superclass, or a interface or related in any way. They are just 2 different classes i would like php map the attributes from a cat class to a dog and give me the new object. –

i guess i have to specify a little bit more cause seem like a senseless thing to do.

i've classes that inherits from different parent classes cause i've made an inheritance tree based on the saving method, maybe my bad from the beginning, but the problem is that i have a lot of classes that are practically equal but interacts one with mysql and the other one with xml files. so i have:

class MySql_SomeEntity extends SomeMysqlInteract{}

and

Xml_SomeEntity extends SomeXmlInteract{}

its a little bit deeper tree but the problem its that. i cant make them inherits from the same class cause multiple inheritance is not allowed, and i cant separate current interaction with superclases cause would be a big trouble.

Basically the attributes in each one are practical the same.

since i have a lot of this matching classes i would like to do some generic casting or something like it that can converts (pass the values to each attribute) and but im trying to search the simplest way to everyone of this classes.

Solution 1:

You can use above function for casting not similar class objects (PHP >= 5.3)

/**
 * Class casting
 *
 * @param string|object $destination
 * @param object $sourceObject
 * @return object
 */
function cast($destination, $sourceObject)
{
    if (is_string($destination)) {
        $destination = new $destination();
    }
    $sourceReflection = new ReflectionObject($sourceObject);
    $destinationReflection = new ReflectionObject($destination);
    $sourceProperties = $sourceReflection->getProperties();
    foreach ($sourceProperties as $sourceProperty) {
        $sourceProperty->setAccessible(true);
        $name = $sourceProperty->getName();
        $value = $sourceProperty->getValue($sourceObject);
        if ($destinationReflection->hasProperty($name)) {
            $propDest = $destinationReflection->getProperty($name);
            $propDest->setAccessible(true);
            $propDest->setValue($destination,$value);
        } else {
            $destination->$name = $value;
        }
    }
    return $destination;
}

EXAMPLE:

class A 
{
  private $_x;   
}

class B 
{
  public $_x;   
}

$a = new A();
$b = new B();

$x = cast('A',$b);
$x = cast('B',$a);

Solution 2:

There is no built-in method for type casting of user defined objects in PHP. That said, here are several possible solutions:

1) Use a function like the one below to deserialize the object, alter the string so that the properties you need are included in the new object once it's deserialized.

function cast($obj, $to_class) {
  if(class_exists($to_class)) {
    $obj_in = serialize($obj);
    $obj_out = 'O:' . strlen($to_class) . ':"' . $to_class . '":' . substr($obj_in, $obj_in[2] + 7);
    return unserialize($obj_out);
  }
  else
    return false;
}

2) Alternatively, you could copy the object's properties using reflection / manually iterating through them all or using get_object_vars().

This article should enlighten you on the "dark corners of PHP" and implementing typecasting on the user level.

Solution 3:

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

Solution 4:

You do not need casting. Everything is dynamic.

I have a class Discount.
I have several classes that extends this class:
ProductDiscount
StoreDiscount
ShippingDiscount
...

Somewhere in the code I have:

$pd = new ProductDiscount();
$pd->setDiscount(5, ProductDiscount::PRODUCT_DISCOUNT_PERCENT);
$pd->setProductId(1);

$this->discounts[] = $pd;

.....

$sd = new StoreDiscount();
$sd->setDiscount(5, StoreDiscount::STORE_DISCOUNT_PERCENT);
$sd->setStoreId(1);

$this->discounts[] = $sd;

And somewhere I have:

foreach ($this->discounts as $discount){

    if ($discount->getDiscountType()==Discount::DISCOUNT_TYPE_PRODUCT){

        $productDiscount = $discount; // you do not need casting.
        $amount = $productDiscount->getDiscountAmount($this->getItemTotalPrice());
        ...
    }

}// foreach

Where getDiscountAmount is ProductDiscount specific function, and getDiscountType is Discount specific function.