Arrays : returning a reference to an array item ??

[Nico]

Hello folks,

I am currently storing a set of objects inside an array,

$itemlist = array();
$itemlist[] = new item("myitem");
//...

and I am looking to develop a search function, which returns a
reference to the found item.

function &search_item($itemlist,"myitem") {
//...
}

I am trying to figure out how to obtain a reference to a given item in
an array.
Indeed, foreach() and each() seem to work on copies of the data in the
array.
For example:

$array = array("a","b","c","d");
print_r($array);
foreach($array as $v) $v="xxx";
print_r($array); // $array is unchanged

reset($array) ; while(list(,$v)=each($array)) $v="xxx";
print_r($array); // $array is unchanged, again

Would you have any idea how to achieve what I am looking for ?
Thanks in advance,
--
NZ

[Ian.H]

On Wed, 11 Aug 2004 06:58:47 -0700, Nico wrote:

Hello folks,

I am currently storing a set of objects inside an array,

$itemlist = array();
$itemlist[] = new item("myitem");
//...

and I am looking to develop a search function, which returns a
reference to the found item.

function &search_item($itemlist,"myitem") {
//...
}

I am trying to figure out how to obtain a reference to a given item in
an array.
Indeed, foreach() and each() seem to work on copies of the data in the
array.
For example:

$array = array("a","b","c","d");
print_r($array);
foreach($array as $v) $v="xxx";
print_r($array); // $array is unchanged

reset($array) ; while(list(,$v)=each($array)) $v="xxx";
print_r($array); // $array is unchanged, again

Would you have any idea how to achieve what I am looking for ?
Thanks in advance,

for ($i = 0; $i < sizeof($array); $i++) {
$array[$i] = 'xxx';
}
This sort of what you're after?

Regards,

Ian

--
Ian.H
digiServ Network
London, UK
http://digiserv.net/

[Nico]

Ian.H wrote:

On Wed, 11 Aug 2004 06:58:47 -0700, Nico wrote:

Hello folks,

I am currently storing a set of objects inside an array,

$itemlist = array();
$itemlist[] = new item("myitem");
//...

and I am looking to develop a search function, which returns a
reference to the found item.

function &search_item($itemlist,"myitem") {
//...
}

I am trying to figure out how to obtain a reference to a given item
in an array.
Indeed, foreach() and each() seem to work on copies of the data in
the array.
For example:

$array = array("a","b","c","d");
print_r($array);
foreach($array as $v) $v="xxx";
print_r($array); // $array is unchanged

reset($array) ; while(list(,$v)=each($array)) $v="xxx";
print_r($array); // $array is unchanged, again

Would you have any idea how to achieve what I am looking for ?
Thanks in advance,

Thank you for your reply,
for ($i = 0; $i < sizeof($array); $i++) {
$array[$i] = 'xxx';
}
This sort of what you're after?

Ok that does it, but this is not my point...
My point is : the examples I gave are just meant to show that foreach(), as
well as list(), make a COPY of the data stored in the array ; modifying the
data does not modify the array content.
What I am looking for is a way to have a REFERENCE on the array item's data,
in order to manipulate this data.

For example:

class foo {
var $name;
var $value;
// etc...
function foo($name, $value) { $this->name = $name ; $this->value=$value; }
}

class foo_bunch {
var $foos=array();
function new_foo($name, $value) {
$foos[] = new foo($name,$value);
}
// search should return a reference on the foo with specified name
function &search($name) {
// go through the $foos[] array, find the name, return a reference
on the foo
foreach($this->foos as $foo) // here $foo is a copy of the array's
item
if($foo->name==$name) return($foo);
return(NULL);
}
}

$my_bunch = new foo_bunch();
$my_bunch->new_foo("lemon","yellow");
$my_bunch->new_foo("tomato","red");
$my_bunch->new_foo("apple","red");
$foo =& $my_bunch->search("apple");
$foo->value = "green";

The point is : return a reference to the array's item (foo), to do whatever
with the data included therein...
Is it clearer this way ?

TIA
--
Nico | http://nzeches.free.fr
Un intellectuel assis va moins loin qu'un con qui marche. (M.Audiard)

[Ian.H]

On Thu, 12 Aug 2004 00:38:50 +0200, Nico wrote:

Ian.H wrote:

On Wed, 11 Aug 2004 06:58:47 -0700, Nico wrote:

Hello folks,

I am currently storing a set of objects inside an array,

$itemlist = array();
$itemlist[] = new item("myitem");
//...

and I am looking to develop a search function, which returns a
reference to the found item.

function &search_item($itemlist,"myitem") {
//...
}

I am trying to figure out how to obtain a reference to a given item
in an array.
Indeed, foreach() and each() seem to work on copies of the data in
the array.
For example:

$array = array("a","b","c","d");
print_r($array);
foreach($array as $v) $v="xxx";
print_r($array); // $array is unchanged

reset($array) ; while(list(,$v)=each($array)) $v="xxx";
print_r($array); // $array is unchanged, again

Would you have any idea how to achieve what I am looking for ?
Thanks in advance,

Thank you for your reply,

for ($i = 0; $i < sizeof($array); $i++) {
$array[$i] = 'xxx';
}
This sort of what you're after?

Ok that does it, but this is not my point...
My point is : the examples I gave are just meant to show that foreach(), as
well as list(), make a COPY of the data stored in the array ; modifying the
data does not modify the array content.
What I am looking for is a way to have a REFERENCE on the array item's data,
in order to manipulate this data.

For example:

class foo {
var $name;
var $value;
// etc...
function foo($name, $value) { $this->name = $name ; $this->value=$value; }
}

class foo_bunch {
var $foos=array();
function new_foo($name, $value) {
$foos[] = new foo($name,$value);
}
// search should return a reference on the foo with specified name
function &search($name) {
// go through the $foos[] array, find the name, return a reference
on the foo
foreach($this->foos as $foo) // here $foo is a copy of the array's
item
if($foo->name==$name) return($foo);
return(NULL);
}
}

$my_bunch = new foo_bunch();
$my_bunch->new_foo("lemon","yellow");
$my_bunch->new_foo("tomato","red");
$my_bunch->new_foo("apple","red");
$foo =& $my_bunch->search("apple");
$foo->value = "green";

The point is : return a reference to the array's item (foo), to do whatever
with the data included therein...
Is it clearer this way ?

TIA

Sorry Nico.. I guess I took your actual example code a little too literal
rather than the actual issue =)

I understand the issue (thought about this a few times myself which is
what immediately made me think of the for() loop). I'm not sure however,
if I actually have a decent answer to give on how / why.

Sorry I can't shed more light on the problem atm but wanted to acknowledge
your reply =)

Regards,

Ian

--
Ian.H
digiServ Network
London, UK
http://digiserv.net/

[Michael Fesser]

.oO(Nico)

The point is : return a reference to the array's item (foo), to do whatever
with the data included therein...
Is it clearer this way ?

<?php
function &searchItem(&$itemList, $name) {
foreach($itemList as $key => $item) {
if ($item['name'] == $name) {
return $itemList[$key];
}
}
return NULL;
}

$foo = array(
array('name' => 'apple', 'color' => 'green'),
array('name' => 'lemon', 'color' => 'yellow')
);

header('Content-type: text/plain');
print_r($foo);
$bar = &searchItem($foo, 'lemon');
$bar['color'] = 'blue';
print_r($foo);
?>
Notice the used '&':
1) The argument $itemList is passed by reference.
2) The search function returns a reference.
3) Assigning the return value to a variable also needs a reference
operator.

HTH
Micha

[Nico]

Michael Fesser wrote:

<?php
function &searchItem(&$itemList, $name) {
foreach($itemList as $key => $item) {
if ($item['name'] == $name) {
return $itemList[$key];
}
}
return NULL;
}
HTH
Micha

This sure helped a lot !
Simple enough, just go back to the source, and forget about the $item, which
is a copy of the array's item
It works great, many thanks...
--
Nico | http://nzeches.free.fr
Un intellectuel assis va moins loin qu'un con qui marche. (M.Audiard)