Problem passing $this by reference

[adamCath]

My code is something like this:

class ClassA
{
  var classb;
  var myvar;
  function ClassA()
  {
    myvar = 1;
    classb = new ClassB($this);
  }
}

class ClassB
{
  var object;
  function ClassB(&$object)
  {
    $this->object = $object;
    $this->object->myvar = 2;
  }
}

If I create an instance of ClassA, myvar will have the value 1. But because ClassA was passed by reference, ClassB should be able to modify the contents of ClassA? What is happening here?

Thanks.

[drew010]

first you need to pass the object by reference in the function call, not the prototype and since you sent in the address of the object. if you want it to maintain the same memory address, you shouldnt try to use the copy constructor (=) on it since that will try to create a new instance of it.

here is code that works

<?php

class ClassA
{
  var $classb;
  var $myvar;
  function ClassA()
  {
    $this->myvar = 1;
    $classb = new ClassB(&$this);
  }
}

class ClassB
{
  function ClassB($object)
  {
    $object->myvar = 2;
  }
} 

$var1 = new ClassA();
echo $var1->myvar; //2

?>

if you want to have a clone of a classA object in classB, you may want to save the trouble of this method and try using extends so classB is a classA and more.

[mrhappiness]

function ClassB(&$object)
{
$this->object = &$object;
$this->object->myvar = 2;
}

this will do the trick

[mrhappiness]

Originally posted by drew010
first you need to pass the object by reference in the function call, not the prototype and since you sent in the address of the object.

no

and i even get a notice telling me that passing vars by reference won't be supported in futre versions of php (or something similar)

if you want to have a clone of a classA object in classB, you may want to save the trouble of this method and try using extends so classB is a classA and more.

no...

at least i don't see no sense having a user-class extending my database class and a menu class extending my database class...

i have one instance of my database class, pass it to user class and menu class (where it is handled as reference of course)

$db = &new db();
$user = &new user($db);
$menu = &new menu($db);

...


$db->output_all_sql();

this way i will get all sql commands being sent to the database from within $user, $menu and of course by the script itself
this won't be possible if all the classes extend my database class since i would have several instances of database class in memory...

and by the way: doing such thing is not the reason why extend has been introduced

[adamCath]

Thanks guys. I fixed the problem with your help. My function was like this

function ClassB( &$object )
{
  $this->myobject = $object;
}

And for some reason $myobject was a copy of $object, though it was being passed by reference. That I don't understand, but using

function ClassB( &$object )
{
  $this->myobject = &$object;
}

fixed the problem. Thanks for the promptness.

[mrhappiness]

function classB(&$object)

makes $object inside function classB to be a reference and not a copy

but without the & in $this->object = $object you do copy th eobject and therefor you stored a copy of the reference of the object that is a copy of the object

got it?