Tree-like structure in PHP?

I'm trying to use arrays to implement a sort of data tree. For the code to
work, it is essential that the nodes can be edited after they have become
part of the tree. That would require that the array elements are pushed
"by reference" rather than "by value".

<?php

$arr1 = array ();
$arr2 = array ();

array_push ($arr1, 1);
array_push ($arr1, $arr2); // <-- the important line
array_push ($arr1, 2);
array_push ($arr2, 3);
array_push ($arr2, 4);

// Contents of $arr2 are now empty
// apparently $arr2 is inserted by value
print_r ($arr1);

echo "Expected output:\n";
$arr1[1] = $arr2;
print_r ($arr1);
?>

What is the most obvious way to implement a tree-like structure in PHP? Is
there a way to push arrays by reference rather than by value?

BTW: I'm using PHP CLI version 5.2

Thanks, the empasant helps!

On 16/11/2007, Paul van Haren <paul.vanharen@zonnet.nl> wrote:
> I'm trying to use arrays to implement a sort of data tree. For the code to
> work, it is essential that the nodes can be edited after they have become
> part of the tree. That would require that the array elements are pushed
> "by reference" rather than "by value".
>
> <?php
>
> $arr1 = array ();
> $arr2 = array ();
>
> array_push ($arr1, 1);
> array_push ($arr1, $arr2); // <-- the important line

array_push ($arr1, &$arr2);
or
$arr1[] =& $arr2;

-robin

Paul van Haren wrote:
> I'm trying to use arrays to implement a sort of data tree. For the code to
> work, it is essential that the nodes can be edited after they have become
> part of the tree. That would require that the array elements are pushed
> "by reference" rather than "by value".
>
> <?php
>
> $arr1 = array ();
> $arr2 = array ();
>
> array_push ($arr1, 1);
> array_push ($arr1, $arr2); // <-- the important line

$arr1[] =& $arr2;

> array_push ($arr1, 2);
> array_push ($arr2, 3);
> array_push ($arr2, 4);
>
> // Contents of $arr2 are now empty
> // apparently $arr2 is inserted by value
> print_r ($arr1);
>
> echo "Expected output:\n";
> $arr1[1] = $arr2;
> print_r ($arr1);
> ?>
>
> What is the most obvious way to implement a tree-like structure in PHP? Is
> there a way to push arrays by reference rather than by value?
>
> BTW: I'm using PHP CLI version 5.2
>

> What is the most obvious way to implement a tree-like structure in PHP?

Use someone elses code that already works. :) Array based tree class is
here:

http://www.phpguru.org/Tree/Tree.phps

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Paul van Haren wrote:
> Thanks, the empasant helps!

ampersand :-)

>