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Re: Object constructors/destructors [message #185097 is a reply to message #185096] Wed, 26 February 2014 13:44 Go to previous messageGo to previous message
Jerry Stuckle is currently offline  Jerry Stuckle
Messages: 2598
Registered: September 2010
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On 2/26/2014 7:50 AM, Richard Damon wrote:
> 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.
>

__wakeup() is not a constructor - and does not do the same thing.

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Jerry Stuckle
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==================
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