PHP, Arrays, and References

Question

Why does the following code not work as I was expecting?

<?php
$data = array(
    array('Area1', null, null),
    array(null, 'Section1', null),
    array(null, null, 'Location1'),
    array('Area2', null, null),
    array(null, 'Section2', null),
    array(null, null, 'Location2')
);
$root = array();
foreach ($data as $row) {
    if ($row[0]) {
        $area = array();
        $root[$row[0]] =& $area;
    } elseif ($row[1]) {
        $section = array();
        $area[$row[1]] =& $section;
    } elseif ($row[2]) {
        $section[] = $row[2];
    }
}
print_r($root);

Expected result:

Array(
    [Area1] => Array(                         
            [Section1] => Array(
                    [0] => Location1
                )                   
        )
    [Area2] => Array(           
            [Section2] => Array(              
                    [0] => Location2
                )                   
        )
)

Actual result:

Array(
    [Area1] => Array(                         
            [Section2] => Array(
                    [0] => Location2
                )                   
        )
    [Area2] => Array(           
            [Section2] => Array(              
                    [0] => Location2
                )                   
        )
)

pix0r · Accepted Answer · 2008-09-04 00:14:23Z

3

If you modify your code on two lines as follows:

$area = array();

$section = array();

to this:

unset($area);
$area = array();

unset($section);
$section = array();

it will work as expected.

In the first version, $area and $section are acting as "pointers" to the value inside the $root array. If you reset the values first, those variables can then be used to create brand new arrays instead of overwriting the previous arrays.

edited Sep 4, 2008 at 0:14

answered Sep 4, 2008 at 0:08

pix0r

31.3k18 gold badges88 silver badges102 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

B. Desai · Accepted Answer · 2017-11-04 08:58:16Z

1

This will also works:

$root[$row[0]] = array();
$area =& $root[$row[0]];

edited Nov 4, 2017 at 8:58

B. Desai

16.4k5 gold badges28 silver badges48 bronze badges

answered Sep 4, 2008 at 0:30

grom

16.2k19 gold badges66 silver badges68 bronze badges

Collectives™ on Stack Overflow

PHP, Arrays, and References

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related