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Re: Object constructors/destructors [message #185096 is a reply to message #185081] Wed, 26 February 2014 12:50 Go to previous messageGo to previous message
Richard Damon is currently offline  Richard Damon
Messages: 58
Registered: August 2011
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On 2/25/14, 4:32 PM, Jerry Stuckle wrote:
> On 2/25/2014 4:19 PM, Christoph Michael Becker wrote:
>> Jerry Stuckle wrote:
>>
>>> On 2/25/2014 2:19 PM, Christoph Michael Becker wrote:
>>>> Jerry Stuckle wrote:
>>>>
>>>> > I have my own problems with PHP - for instance, it is entirely
>>>> > possible
>>>> > to create an object without calling a constructor - a violation of OO
>>>> > principles. But I work around it.
>>>>
>>>> How is it possible to create an object without its constructor (if
>>>> defined) being called?
>>>>
>>>
>>> Load the object from the $_SESSION. The constructor will not be called.
>>>
>>> However, the constructor is called when the original object was created,
>>> and the destructor called when the original object goes out of scope.
>>> The destructor is also called when the object loaded from the $_SESSION
>>> goes out of scope.
>>>
>>> The result is one constructor call and two destructor calls. A
>>> violation of OO principles.
>>
>> Um, I'm not sure whether this is a violation of OOP principles. Storing
>> an object in the session requires serialization of the object, what is
>> somewhat comparable to cloning an object. So actually, you're not
>> working with the *same* object.
>>
>> Anyway, you can work around these issues by using the magic methods
>> __sleep() and __wakeup(), as you probably know. :)
>>
>
> Yes, it is a violation. When the script starts, the object is
> serialized in the $_SESSION. But it does not exist in the script.
> Creating it requires a constructor call. OO principles require exactly
> one constructor call and one destructor call for every object created.
> Note these may be explicit or implicit, and the functions may be noops,
> but the calls must still be made. That is not the case here; you get
> one constructor call and two destructor calls.
>
> I know of no other OO language which would allow this.
>

An the "name" of the Deserializing constructor in PHP is __wakeup().

You also do NOT get two destructor calls on the same object, the
deserializing created a new object.
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