Variables in Classes Question

[renj0806]

How can i make a variable in my class not change its value after it is declared. Take for example the code below:

 

Datamanager.php

$datamanager = new DataManager();

Class DataManager {
  var $index = 0;
  
  function DataManager(){
  }

  function incrementIndex(){
    $this->index++;
  }

  function getIndex(){
    return $this->index;
  }
}

 

In my first php page i include("Datamanager.php"), everything works fine if i do things in one page. If i incrementIndex() 5 times then the value of getIndex() returns 5. However, i face a problem when i do it in another page where i include("Datamanager.php") again because an error occurs when i dont include it. When i getIndex() in a second php page after doing an incrementIndex() 5x on the other page, the value returned by getIndex() is back to 0. Can anyone explain to me why?

 

Or can anyone give me a sample wherein the returned value of getIndex() will not be back to 0?  Please...Thanks!

[Balmung-San]

I'll try to explain to you why that happens in something of an example. Think of a class declaration as a recipe.

 

Now, when you include the page you're baking a cake following the recipe. (Creating an object via new ClassName()).

 

Every time you go to a page a new cake is baked, this is because the cake (Created Object)from the last page isn't get passed over. Objects (cakes) are garbaged after that page is done, unless you store them somewhere.

 

Does that make sense, or am I just talking like a crazy person?

[renj0806]

That made sense. And i also knew that was the reason. But im still new at PHP and i cant find any other way to improvise my current codes. I just dont know a solution thats why Im bringing it up in this forums for some experts like you to suggest something.

 

Thanks for you analogy btw. 

[Balmung-San]

Things you can do are to save the object in the session, which I'm against, but maybe that's just me.

 

You could also save out the necessary variables to a cookie, a session, or a database, and retrieve it on the next page.

[renj0806]

A session, im not into it also.

 

A cookie, that i dont know. Coz i also have a multidimensional array within my class so i think those things wont work for it, right?

 

As for database, its not worth it.  Takes up space and its not really important to be stored in a database. 

[Balmung-San]

Actually, from what I've heard cookies play really nicely with PHP arrays, though I've never done it myself.

[renj0806]

Oh I see. Im gonna look into cookies. But for anyone there who knows how to handle such arrays in cookies. Please do post an example. It would really help.

 

Thanks for you help Balmung-San. Im gonna sleep now and do things again tomorrow. Im hoping some examples will be posted. See ya!

[renj0806]

Anyone have an example how to incorporate an array into cookies? Please do post an example please. Thanks!

 

And another question, can cookies solve my problems Ive said above?

[trq]

Easiest way would be to serialize it first but honestly, unless you need to keep this object persistent for long periods of time, sessions are the way to go. They automatically serialize the data for you and are simple to use.

[renj0806]

Ok, so im gonna use sessions. And arrays can be stored in sessions right? How can arrays be retreived in sessions?

 

$_SESSION['session_name'][1] ? Do I have the right syntax?

[trq]

I thought you wanted to store objects?

[trq]

A simple example. 3 pages.

 

foo.class.php

<?php

  class foo {
    public $a = 1;

    function inca() {
      $this->a++
    }

?>

 

p1.php

<?php

  session_start();
  include 'foo.class.php';

  $f = new foo();
  echo $f->a;
  $f->inca();
  $_SESSION['foo'] = $f;
  echo "<a href='p2.php'>next</a>";

?>

 

p2.php

<?php

  session_start();
  include 'foo.class.php';

  $f = $_SESSION['foo']
  echo $f->a;
  $f->inca();
  echo $f->a;

?>

[renj0806]

For example if my object was an array type, how would i do that?

[renj0806]

A simple example. 3 pages.

 

foo.class.php

<?php

  class foo {
    public $a = 1;

    function inca() {
      $this->a++
    }

?>

 

p1.php

<?php

  session_start();
  include 'foo.class.php';

  $f = new foo();
  echo $f->a;
  $f->inca();
  $_SESSION['foo'] = $f;
  echo "<a href='p2.php'>next</a>";

?>

 

p2.php

<?php

  session_start();
  include 'foo.class.php';

  $f = $_SESSION['foo']
  echo $f->a;
  $f->inca();
  echo $f->a;

?>

 

what if i set $a as an array variable?

 

foo.class.php

<?php

  class foo {
    public $a = array("Hello","World");

    function conca() {
      $this->a[] = a[] . "Everyone"
    }

?>

 

How can I echo $a after putting it in a $_SESSION['foo'] just like in p1.php i quoted above?

[Jessica]

$foo = $_SESSION['foo'];

print_r($foo->a);

Just like you normally would