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                 )                            ) ) 

Answer 1

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.