Confusion about classes and objects

[laredotornado@zipmail.com]

Hi,

Using PHP 4.4.4, I have a class defined like so

class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserTOCItem($p _id)
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren
} // CUserItem

then in a separate bit of code, I have an associative array of
objects, with the key being the id and the value being the object.
Unfortunately, when I try and manipulate the objects in the array, it
doesn't take ...

$item = new CUserItem(1);
$item2 = new CUserItem(2);
$toc_items_arr[1] = $item;
$item->addChild($item 2);
print $toc_items_arr[1]-

>numChildren( ); // still prints zero!

The "print" line should print out "1" because I have added a child.
But it does not. What's going wrong? - Dave

[Mike Roetgers]

Re: Confusion about classes and objects

laredotornado@z ipmail.com schrieb:

Hi,
>
Using PHP 4.4.4, I have a class defined like so
>
class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserTOCItem($p _id)
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren
} // CUserItem
>
then in a separate bit of code, I have an associative array of
objects, with the key being the id and the value being the object.
Unfortunately, when I try and manipulate the objects in the array, it
doesn't take ...
>
$item = new CUserItem(1);
$item2 = new CUserItem(2);
$toc_items_arr[1] = $item;
$item->addChild($item 2);
print $toc_items_arr[1]-

>numChildren( ); // still prints zero!

>
The "print" line should print out "1" because I have added a child.
But it does not. What's going wrong? - Dave
>

I don't see a constructor in your class. When you're working with PHP4,
you must name the constructor like the class:

class CUserItem {
function CUserItem($valu e)
{}
}

[laredotornado@zipmail.com]

Re: Confusion about classes and objects

On Mar 1, 9:38 am, Mike Roetgers <miker...@infor matik.uni-bremen.de>
wrote:

laredotorn...@z ipmail.com schrieb:
>

Hi,

>

Using PHP 4.4.4, I have a class defined like so

>

class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserTOCItem($p _id)
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren
} // CUserItem

>

then in a separate bit of code, I have an associative array of
objects, with the key being the id and the value being the object.
Unfortunately, when I try and manipulate the objects in the array, it
doesn't take ...

>

$item = new CUserItem(1);
$item2 = new CUserItem(2);
$toc_items_arr[1] = $item;
$item->addChild($item 2);
print $toc_items_arr[1]-

numChildren(); // still prints zero!

>

The "print" line should print out "1" because I have added a child.
But it does not. What's going wrong? - Dave

>
I don't see a constructor in your class. When you're working with PHP4,
you must name the constructor like the class:
>
class CUserItem {
function CUserItem($valu e)
{}
>
}

Excuse me, I rewrote my code to make a little more sense on the
newsgroup but forgot to change a couple of things. here is the classs

class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserItem($p_id )
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren
} // CUserItem

Please consider this class in the question posed above. -

[=?ISO-8859-15?Q?Iv=E1n_S=E1nchez_Ortega?=]

Re: Confusion about classes and objects

$item = new CUserItem(1);

$item2 = new CUserItem(2);
$toc_items_arr[1] = $item;
$item->addChild($item 2);
print $toc_items_arr[1]->numChildren( ); // still prints zero!
>
The "print" line should print out "1" because I have added a child.
But it does not. What's going wrong? - Dave

You're assigning a copy og $item to $toc_items_arr[1], not a reference to
$item.

Thus, you are updating $item but not $toc_items_arr[1].

Please re-read the chapter on references in the PHP manual; after you've
done so, you'll probably understand what's going on. And then, by RTFM,
you'll learn to assing things by reference.

--
----------------------------------
Iván Sánchez Ortega -ivansanchez-algarroba-escomposlinux-punto-org-

Un ordenador no es un televisor ni un microondas, es una herramienta
compleja.

[Mark Babli]

Re: Confusion about classes and objects

laredotornado@z ipmail.com wrote:

Hi,
>
Using PHP 4.4.4, I have a class defined like so
>
class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserTOCItem($p _id)
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren
} // CUserItem
>
then in a separate bit of code, I have an associative array of
objects, with the key being the id and the value being the object.
Unfortunately, when I try and manipulate the objects in the array, it
doesn't take ...
>
$item = new CUserItem(1);
$item2 = new CUserItem(2);
$toc_items_arr[1] = $item;
$item->addChild($item 2);
print $toc_items_arr[1]-

>numChildren( ); // still prints zero!

>
The "print" line should print out "1" because I have added a child.
But it does not. What's going wrong? - Dave
>

Hello,

The error message I got was: "Fatal Error: Object of type CUserItem
could not be converted into a string". The modified code works.


class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserItem($p_id )
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren

// ADDED this function to print the identity
function print_me(){
print $this->m_id;
} // added this new function
} // CUserItem


$item = new CUserItem(1);
$item2 = new CUserItem(2);
$toc_items_arr[1] = $item;
$item->addChild($item 2);
$toc_items_arr[1]->print_me(); // Now it prints 1

Hope this helps.

[Hendri Kurniawan]

Re: Confusion about classes and objects

laredotornado@z ipmail.com wrote:

On Mar 1, 9:38 am, Mike Roetgers <miker...@infor matik.uni-bremen.de>
wrote:

>laredotorn...@ zipmail.com schrieb:
>>

>>Hi,
>>Using PHP 4.4.4, I have a class defined like so

>> $item = new CUserItem(1);
>> $item2 = new CUserItem(2);
>> $toc_items_arr[1] = $item;
>> $item->addChild($item 2);
>> print $toc_items_arr[1]-
>>>numChildren( ); // still prints zero!
>>The "print" line should print out "1" because I have added a child.
>>But it does not. What's going wrong? - Dave

>I don't see a constructor in your class. When you're working with PHP4,
>you must name the constructor like the class:

>
class CUserItem {
var $m_id;
var $m_children_arr ;
function CUserItem($p_id )
{
$this->m_id = $p_id;
$this->m_children_a rr = array();
} // CUserItem
function addChild($p_chi ld) {
array_push($thi s->m_children_arr , $p_child);
} // addChild
function numChildren() {
return count($this->m_children_arr );
} // numChildren
} // CUserItem
>
Please consider this class in the question posed above. -
>

You are using PHP4, threfore when assigning object to a variable,
you should use an assign reference (ie. =&)

So instead of:
$toc_items_arr[1] = $item;
use:
$toc_items_arr[1] =& $item;


This makes sure that the line:
print $toc_items_arr[1]->numChildren( );
refers to the one and original $item

Hendri Kurniawan

[Toby A Inkster]

Re: Confusion about classes and objects

Iván Sánchez Ortega wrote:

You're assigning a copy og $item to $toc_items_arr[1], not a reference to
$item.

This is almost certainly the problem.

Note that in PHP 5 the default behaviour of the assignment operator is
changed with respect to how it operates on objects, and is closer to the
Java behaviour which is what I think you were expecting.

PHP 4:

<?php
$a = new Object();
$b = $a;
// Variables $a and $b point to two different objects.
// Changes to $a do not effect $b.
?>

PHP 5:

<?php
$a = new Object();
$b = $a;
// Variables $a and $b point to the same object.
// Changes to $a effect $b.
?>

--
Toby A Inkster BSc (Hons) ARCS
Contact Me ~ http://tobyinkster.co.uk/contact
Geek of ~ HTML/SQL/Perl/PHP/Python*/Apache/Linux

* = I'm getting there!