note 48730 modified in language.types.array by nforbes
| From: | nforbes@php.net | Date: | Fri, 18 Aug 2006 21:51:19 +0000 |
| Subject: | note 48730 modified in language.types.array by nforbes | ||
| References: | 1 | Groups: | php.notes |
| Request: | Send a blank email to php-notes+get-116045@lists.php.net to get a copy of this message | ||
[Editor's Note: (Second example.) These are not "arrays in arrays". These are
single-dimensional arrays containing stdClass objects; all objects are referenced by default in
PHP5. You can see in the var_dump output that they point to the same object.]
Attention with Arrays in Arrays!
If you copy (=) an array which contains arrays it will be REFERENCED not COPIED.
Example:
<?php
/* GOOD ONE */
echo "<b>Here copy (=) works correct:</b><br>";
/* Initialise Array 1 */
$x1 = array(array(10,20),array(30,40));
/* COPY Array */
$x2 = $x1;
/* Change some values in Array 2 */
$x2[0][0]=77;
$x2[1][1]=99;
echo "<b>Original:</b><pre>";
var_dump($x1);
echo "</pre><b>Changed Copy:</b><pre>";
var_dump($x2);
/* BAAAAAAAD ONE */
echo "</pre><hr><b>Here copy (=) FAILS:</b><br>";
/* Initialise Array 1 */
$a1[0]->bla[0]->id=10;
$a1[0]->bla[1]->id=20;
$a1[1]->bla[0]->id=30;
$a1[1]->bla[1]->id=40;
/* COPY Array */
$a2 = $a1;
/* Change some values in Array 2 (!) */
$a2[0]->bla[0]->id=77;
$a2[1]->bla[1]->id=99;
echo "<b>Original:</b><pre>";
var_dump($a1);
echo "</pre><b>Changed Copy:</b><pre>";
var_dump($a2);
echo "</pre>";
php?>
The output of $a1 and $a2 will be the same..
--was--
Attention with Arrays in Arrays!
If you copy (=) an array which contains arrays it will be REFERENCED not COPIED.
Example:
<?php
/* GOOD ONE */
echo "<b>Here copy (=) works correct:</b><br>";
/* Initialise Array 1 */
$x1 = array(array(10,20),array(30,40));
/* COPY Array */
$x2 = $x1;
/* Change some values in Array 2 */
$x2[0][0]=77;
$x2[1][1]=99;
echo "<b>Original:</b><pre>";
var_dump($x1);
echo "</pre><b>Changed Copy:</b><pre>";
var_dump($x2);
/* BAAAAAAAD ONE */
echo "</pre><hr><b>Here copy (=) FAILS:</b><br>";
/* Initialise Array 1 */
$a1[0]->bla[0]->id=10;
$a1[0]->bla[1]->id=20;
$a1[1]->bla[0]->id=30;
$a1[1]->bla[1]->id=40;
/* COPY Array */
$a2 = $a1;
/* Change some values in Array 2 (!) */
$a2[0]->bla[0]->id=77;
$a2[1]->bla[1]->id=99;
echo "<b>Original:</b><pre>";
var_dump($a1);
echo "</pre><b>Changed Copy:</b><pre>";
var_dump($a2);
echo "</pre>";
php?>
The output of $a1 and $a2 will be the same..
http://php.net/manual/en/language.types.array.php