ordering categories with php arrays - php

Question

I have an array of categories:
categories = computers, entertainment, products, graphics cards
The array is sometimes returned in the wrong order BUT each category has a parent which exists in the SAME array.
categories =
products[parent=0],
entertainment[parent=products],
computers[parent=entertainment],
graphics cards[parent=computers]
How would I use php to sort this array if it was returned in any order?
Unordered Example:
categories =
computers[parent=entertainment],
entertainment[parent=products],
products[parent=0],
graphics cards[parent=computers]
Must produce:
categories = products, entertainment, computers, graphics cards

Answer 1

Are you talking about a simple sort like this:
<?php
$categories = array('computers[parent=entertainment]',
'entertainment[parent=products]',
'products[parent=0]',
'graphics cards[parent=computers]');
sort($categories);
echo '<pre>';
print_r($categories);
echo '</pre>';
?>

Answer 2

Looking at your example, I'm assuming you want a topological sort, as Sam Dufel says.
$categories = array(
"computers" => array("parent" => "entertainment"),
"entertainment" => array("parent" => "products"),
"products" => array("parent" => null),
"graphics cards" => array("parent" => "computers")
);
// Set distances
foreach ($categories as $cat => &$e) {
$e["dist"] = nodeDistance($cat, $categories);
}
// Before
echo implode(", ", array_keys($categories)) . "\n";
// Sort
uasort($categories, "nodeDistanceSorter");
// After
echo implode(", ", array_keys($categories)) . "\n";
function nodeDistance($node, $categories) {
// Check cache
if (array_key_exists("dist", $categories[$node]))
return $categories[$node]["dist"];
// Check root
if (is_null($categories[$node]["parent"]))
return 0;
// Traverse
return nodeDistance($categories[$node]["parent"], $categories) + 1;
}
function nodeDistanceSorter($a, $b) {
$aDist = $a["dist"];
$bDist = $b["dist"];
if ($aDist == $bDist)
return 0;
return $aDist - $bDist;
}

Answer 3

categories =
products[parent=0],
entertainment[parent=products],
computers[parent=entertainment],
graphics cards[parent=computers]
I take it that the array is like this:
$categories = array
(
'products'=>array('parent'=>0),//poor little orphan
'entertainment'=>array('parent'=>'products'),
'computers'=>array('parent'=>'entertainment'),
'graphics cards'=>array('parent'=>'computers'),
)
here is a solution that I mixed up right now:
Solution 1
$categories = array
(
'computers'=>array('parent'=>'entertainment'),
'entertainment'=>array('parent'=>'products'),
'products'=>array('parent'=>0),
'graphics cards'=>array('parent'=>'computers')
);
function addparentfirst(&$original,$array,$name,$data){
if(isset($data['parent']) && isset($original[$data['parent']])){
$array = addparentfirst($original,$array,$data['parent'],$original[$data['parent']]);
}
$array[$name] = $data;
unset($original[$name]);
return $array;
}
foreach($categories as $key=>$value){//goes over each category only once, contrary to what it looks like
$sortedcategories = addparentfirst($categories,$sortedcategories,$key,$value);
}
$categories = $sortedcategories;//NOW IT'S SORTED
print_r($categories);
Solution 2
//It's interesting that it doesn't loop infinitely
//I like this solution the most
function addparentfirst(&$array,$key){
if(isset($array[$key]['parent']) && !empty($array[$key]['parent'])){
addparentfirst($array,$array[$key]['parent']);
}
$data = $array[$key];
unset($array[$key]);
$array[$key] = $data;
return $array;
}
foreach($categories as $key=>$value){
addparentfirst($categories,$key);
}
print_r($categories);
Solution 3
function sortArrayByArray($array,$orderArray) {
$ordered = array();
foreach($orderArray as $key) {
if(isset($array[$key])) {
$ordered[$key] = $array[$key];
unset($array[$key]);
}
}
return $ordered + $array;
}
//Usage:
$categories = sortArrayByArray($categories,array('products','entertainment','computers','graphics cards'));
print_r($categories);
as seen here
Solution 4
function get_childless_category_name($array){
foreach($array as $key=>$value){
if(isset($value['parent']) && !empty($value['parent'])){
unset($array[$value['parent']]);
}
}
$names = array_keys($array);//names of all the child free categories
return array_pop($names);//get the last one (there should only be one)
}
function parent_comes_first(&$array,$key){
if(isset($array[$key]['parent']) && !empty($array[$key]['parent'])){
$array = parent_comes_first($array,$array[$key]['parent']);
}
$data = $array[$key];
unset($array[$key]);
$array[$key] = $data;
return $array;
}
//Usage:
$childless = get_childless_category_name($categories);
parent_comes_first($categories,$childless);
print_r($categories);