Destroying a class object

captainmerton · 05-16-2009, 12:48 PM

Quick question about best practice:

When i create an object i use the standard contructor method. Is there an equivalent for destroying an object? If so what is it? If not, what is best practice - should i be destroying objects when i have finished with them?

Cheers,

Capt Merton

allworknoplay · 05-16-2009, 01:19 PM

Quote:

Originally Posted by captainmerton

Quick question about best practice:

When i create an object i use the standard contructor method. Is there an equivalent for destroying an object? If so what is it? If not, what is best practice - should i be destroying objects when i have finished with them?

Cheers,

Capt Merton

You can use the __destruct() construct. The only difference with having one in your class and not having one is that if you don't have one, PHP will destroy your object at the end of the executed script.

As long as there are no more references to the object it will get destroyed.

Salathe · 05-16-2009, 01:38 PM

Just use unset() as you would any other variable.

Village Idiot · 05-16-2009, 02:34 PM

You generally don't have to worry about memory management in PHP, scripts just don't run long enough for leaks to be a problem. This is not always the case in extremely complicated tasks though,

captainmerton · 05-16-2009, 07:08 PM

I'm trying to use it for a logout method in a login class. So when someone is logged in (stored in session) and want to logout i want to kill the session and the class. having problems clearing out the session though.

Wildhoney · 05-16-2009, 08:01 PM

How about clearing the session on the __destruct?

php Code:

class TalkPHP_Login
{
    public function __destruct()
    {
        session_destroy();
        unset($_SESSION);
    }
}

$pLogin = new TalkPHP_Login();
unset($pLogin);

allworknoplay · 05-16-2009, 08:21 PM

Quote:

Originally Posted by Wildhoney

How about clearing the session on the __destruct?

php Code:

class TalkPHP_Login
{
    public function __destruct()
    {
        session_destroy();
        unset($_SESSION);
    }
}

$pLogin = new TalkPHP_Login();
unset($pLogin);

What's the significance of calling session_destroy() before using unset() ??

gregor171 · 05-16-2009, 11:01 PM

I came into PHP from other "more" OOP languages and a practice there is to destroy object by:
$my_object = null;
It's a good habit.

The usage of destructor is to clean object before it's destroyed. That would be to close database connections (that could stay open and this is a bad thing to happen), write some logs etc.

Quote:

Originally Posted by Wildhoney

public function __destruct()
{
session_destroy();
unset($_SESSION);
}

[/highlight]

this won't quite work! variables must be accessible and unset does nothing here.

PHP Code:


			
public function __destruct(){

             global $_SESSION;

        session_destroy();

        unset($_SESSION);

}

Generally clearing the session in destructor seems a good idea, but be careful that this is done on logout only.

allworknoplay · 05-16-2009, 11:17 PM

Quote:

Originally Posted by gregor171

PHP Code:


			
public function __destruct(){

             global $_SESSION;

        session_destroy();

        unset($_SESSION);

}

Generally clearing the session in destructor seems a good idea, but be careful that this is done on logout only.

Interesting, but why do you have to define the $_SESSION globally when it's already a super global array?

Salathe · 05-16-2009, 11:54 PM

Quote:

Originally Posted by Wildhoney

How about clearing the session on the __destruct?

php Code:

class TalkPHP_Login
{
    public function __destruct()
    {
        session_destroy();
        unset($_SESSION);
    }
}

$pLogin = new TalkPHP_Login();
unset($pLogin);

Why would anyone want to destroy the session at the end of every request (which uses that class)?

Quote:

Originally Posted by allworknoplay

What's the significance of calling session_destroy() before using unset() ??

They both do different things. session_destroy destroys data associated with the session, which by default deletes the session file. unset simply unsets the $_SESSION variable.

Quote:

Originally Posted by gregor171

variables must be accessible and unset does nothing here.

PHP Code:


			
public function __destruct(){
             global $_SESSION;
        session_destroy();
        unset($_SESSION);
}

The $_SESSION is what's termed "superglobal" in PHP meaning that it is available in any scope. As such, there is no need to use the global keyword as above.

Wildhoney · 05-16-2009, 11:46 PM

It all depends how you're using your classes, of course, because __destruct will also be called when the script is ended naturally.

gregor171 · 05-17-2009, 12:02 AM

PHP Code:


			
Interesting, but why do you have to define the $_SESSION globally when it's already a super global array?

Sorry! It's a habit

captainmerton · 05-17-2009, 08:52 AM

Thanks for all your comments guys.