TalkPHP - When is __destruct() called?

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Jenski

07-15-2008 10:34 AM

When is __destruct() called?

Hi,
I'm I've been programming in PHP4 for a few years now and am slowly moving over to PHP5, I was wondering when developing a class when the __destruct() function is called? I have put all my closing connections in it, and tried to print to screen for confirmation but it doesn't print anything.

Any thoughts?

Thanks in advance

Karl	07-15-2008 02:31 PM

It is called when you destroy the object. So, for example:

php Code:

class Destruct_Example
{
    public function __construct()
    {
        echo "Called Construct()";
    }
    
    public function __destruct()
    {
        echo "Called Destruct()";
    }
}

$pExample = new Destruct_Example();
unset($pExample);

And it will also be called at the end of the script.

Ross	07-15-2008 02:51 PM

It's quite useful in database abstraction classes, for example:

PHP Code:


		
			
abstract class Database
{
    public function __construct()
    {
        $this->connect();
    }
    
    abstract public function connect();
    /*...*/
    
    public function __destruct()
    {
        $this->conn->close();
    }
}

(although on second thoughts closing it on script exit isn't a huge memory saving :P).

xenon

07-15-2008 06:26 PM

The destructor is always called when the object is destroyed, set to null, or to another data type. If you don't do any of the above specified operations, the destructor will be automatically called after the script has ended (finished processing).

Jenski

08-04-2008 09:16 AM

Is it always called when the script has ended though?

Any reason why it doesn't?

xenon

08-04-2008 06:17 PM

Well, technically, no. The destructor is called when the script has ended, but the memory allocated for the object remains allocated until the garbage collector comes and wipes everything related to the php that's not used anymore. If you were asking if objects are persistent from one page to another, then no. Nothing in PHP is persistent, as all cgi modules use the HTTP protocol as a foundation to run on. And HTTP is a stateless protocol, as we all have learned.

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