php variable scope in oop

Question

I wonder if anyone can help out here, I'm trying to understand how use an objects properties across multiple non class pages,but I can't seem to be able to get my head around everything i have tried so far.

For example a class called person;

class person {
 static $name;     
}

but i have a number of different regular pages that want to utilize $name across the board.

I have trying things like this;

pageone.php

include "person.php";
$names = new Person();

echo person::$name;
names::$name='bob';

pagetwo.php

include "person.php";
echo person::$name;

I can work with classes to the extent I'm OK as long as I am creating new instances every page, but how can make the properties of one object available to all, like a shared variable ?

Thanks

Pekka · Accepted Answer · 2010-03-13 19:45:05Z

3

Every new instance of a PHP script "forgets" everything done in previous scripts. The usual way of establishing a "storage room" for data across page loads is sessions. A session is essentially a specific ID a user gets when visiting a page. That ID is stored in a cookie, or a GET variable that is appended to every URL. PHP keeps text files in a special directory that can contain session specific data. Every file is named using the session ID.

The PHP manual has a thorough introduction here.

pageone.php

session_start();
$_SESSION["name"] = "Bob",

pagetwo.php

session_start();

echo $_SESSION["name"];  // Bob

Now if you had an instantiated object, you could serialize it, store it in a session variable, and unserialize it back in the 2nd page. I don't think that can be done with static classes though. But this should be a good start.

answered Mar 13, 2010 at 19:45

Pekka

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2 Comments

Decent Dabbler Over a year ago

@Pekka: instances don't need to be serialized. PHP session usually does automatic serialization already, as per the ini setting: session.serialize_handler = php

mr o Over a year ago

Thanks, I will look at using session vars

Decent Dabbler · Accepted Answer · 2010-03-13 20:31:04Z

0

You need to initialize the static variable inside the class declaration itself:

class Person {
    public static $name = 'bob';
}

Or, you need some bootstrapping mechanism, where you inititalize the static variable:

bootstrap.php:

Person::$name = 'bob';

and then in the pages:

// assuming, you preloaded the bootstrap somewhere first
$person = new Person();

~~echo $person::$name;~~

edit
Ugh, what was I thinking... the above won't even work. You can't access a static member like that on an instance. Only through a method, like so:

class Person
{
    public static $name;

    public function getName()
    {
        return self::$name;
    }

}

// assuming, you preloaded the bootstrap somewhere first
$person = new Person();
echo $person->getName();

/end edit

Or as Pekka pointed out, use sessions to keep state.

But more importanty: what is the goal you are trying to achieve? If you want to maintain state of a Person object between different requests, then Pekka's route is the way to go, or alternatively use another persistance storage mechanism, like a DB, File, etc...

Because I presume you don't mean to have every single Person instance named 'bob' do you? I presume you mean to maintain state of a single Person instance.

So, concluding, you probably don't want to use a static member to begin with.

edited Mar 13, 2010 at 20:31

answered Mar 13, 2010 at 19:48

Decent Dabbler

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1 Comment

mr o Over a year ago

thanks, it looks like i need to use sessions. The code above was more of an example - I was getting a little confused over oop, i thought that once you create an instance of an object - it's sat in memory, with all it's properties. I was trying to figure out how to access the properties of one instance across different regular php pages.

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