PLZ HELP! Why does my variable print it's value without me telling it to?

Paul_help_

Hi friends.
I have been learning about objects as of late, and I am stumped/confused by something.

here is the code:

class User {
public function __wakeup() {
echo "Yawn... what’s for breakfast? <br/>";
}
}
$user = new User;
$userString = serialize( $user );
$obj = unserialize( $userString );

Simple enough, but what I don't understand is - why, when i run this line:

$obj = unserialize( $userString );

....... for some reason the value of:

"Yawn... what’s for breakfast?"

.... is outputted to my browser.

I don't understand why this would happen when $obj is a variable.

I haven't even used print_r() with the variable $obj to output the value $obj contains.

So why on earth is $obj echoing the value when at first glance it appears merely as a container of the value that is outputted?

Paul.

NogDog

Read http://php.net/manual/en/language.oop5.magic.php#object.sleep about what sleep() and wakeup() do and when they get called, and I think you'll figure it out.

dalecosp

It keeps hurting when I poke myself with a toothpick ...anyone know why? 😉

sneakyimp

The idea of object serialization might be a bit of a mind-boggler at first. This is a pretty clear definition:

Wikipedia wrote:
serialization is the process of translating data structures or object state into a format that can be stored (for example, in a file or memory buffer, or transmitted across a network connection link) and reconstructed later in the same or another computer environment.

The [man]wakeup[/man] function in your code is what is called a "magic method." Magic methods are special methods that get automatically called under certain circumstances. For instance, call() gets invoked when some code tries to call an object method that does not exist. get() is invoked when some code tries to access an object property that does not exist (or is inaccessible). The wakeup method in your code gets invoked when you [man]unserialize[/man] an instance of your class that was previously [man]serialize[/man]d.

It's a pretty well-named function. Think of a serialized object as one that is in suspended animation -- like a frozen caveman or like Jake Sully in Avatar. When you unserialize an object -- i.e., you bring it back from hibernation -- it is 'waking up'. The __wakeup function gets called at that point which gives you an opportunity to have your object orient itself should it need to. It might want to check on the status of some other data, for instance. Or make itself available as a service or something.