如何基于主键和外键输出数组

Question

Considering this array

Array
(
[0] => Array
    (
        [id] => 51
        [category_id] => 37
        [title] => Sims
    )

[1] => Array
    (
        [id] => 37
        [category_id] => 26
        [title] => Blackberry
    )

[2] => Array
    (
        [id] => 26
        [category_id] => 0
        [title] => Mobile Device
    )

I would like to be able to print out:

Mobile Device > Blackberry > Sims

Based on the relationship between category_id and id.

Answer 1

<?php

$array = Array(
    array('id' => 51, 'category_id' => 37, 'title' => 'Sims'),
    array('id' => 37, 'category_id' => 26, 'title' => 'Blackberry'),
    array('id' => 26, 'category_id' => 0, 'title' => 'Mobile Device'));

// First build an associative array ID->Object
$map = array();
foreach( $array as $value )
{
  $map[$value['id']] = $value;
}

// Then build your path
$path = array();
$value = $array[0];
while( true )
{
    $path[] = $value['title'];
    if( $value['category_id'] == 0 )
    {
        break;
    }
    $value = $map[$value['category_id']];
    if( !isset($value) )
    {
        die("Data Inconsistency");
    }
}


// Display path
echo implode(array_reverse($path), ' > ');

?>