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PHP function to cast an object from one class to another.
* Cast an object into a different class.
* Currently this only supports casting DOWN the inheritance chain,
* that is, an object may only be cast into a class if that class
* is a descendant of the object's current class.
* This is mostly to avoid potentially losing data by casting across
* incompatable classes.
* @param object $object The object to cast.
* @param string $class The class to cast the object into.
* @return object
function cast($object, $class) {
if( !is_object($object) )
throw new InvalidArgumentException('$object must be an object.');
if( !is_string($class) )
throw new InvalidArgumentException('$class must be a string.');
if( !class_exists($class) )
throw new InvalidArgumentException(sprintf('Unknown class: %s.', $class));
if( !is_subclass_of($class, get_class($object)) )
throw new InvalidArgumentException(sprintf(
'%s is not a descendant of $object class: %s.',
$class, get_class($object)
* This is a beautifully ugly hack.
* First, we serialize our object, which turns it into a string, allowing
* us to muck about with it using standard string manipulation methods.
* Then, we use preg_replace to change it's defined type to the class
* we're casting it to, and then serialize the string back into an
* object.
return unserialize(
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To initialize properties on the new object that didn't exist in the old one (if the new extends the old), its class definition needs to have a __wakeup() method as unserialize doesn't call __construct().

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