John Davidson

Message:

I am trying to create a new associative array where categories contain multiple items. My input array has the opposite orientation where individual items refer to multiple categories.

Input:

$items = [

    ["itemName" => "Hat", "price" => 10.99, "categories" => ["apparel", "head"]],

    ["itemName" => "Scarf", "price" => 7.99, "categories" => ["apparel", "neck"]],

    ["itemName" => "Watch", "price" => 19.99, "categories" => ["jewelry", "electronics"]],

    ["itemName" => "Necklace", "price" => 99.99, "categories" => ["jewelry", "neck"]],

    ["itemName" => "Headphones", "price" => 29.99, "categories" => ["head", "electronics"]]

];

Desired result:

[

  'apparel' => ['Hat', 'Scarf'],

  'head' => ['Hat', 'Headphones'],

  'neck' => ['Scarf', 'Necklace'],

  'jewelry' => ['Watch', 'Necklace'],

  'electronics' => ['Watch', 'Headphones']

]

My code:

include_once("./array.php");

    

$categories = [];

$categoryMap=array();

#map to find with the category as the key then the item as the value 

foreach ($items as $key => $value) {

    # code...

    $currentCategories = $value['categories'];

    for ($i = 0; $i < sizeof($currentCategories); $i++) {

        # code...

        // if not in keys for the categoryMap then initialize with the key with a value of an empty array

        // otherwise just add the the array of values using that keys

        

        // visual of how it should be 

        // [

        //     'buger':['bun','tomato','sauce']



        // ]

        

        array_push($categories, $currentCategories[$i]);

    }

}

$categories = array_unique($categories);

---

My Answer:
'item1' => ['category1', 'category2'],
'item2' => ['category2', 'category3'],
'item3' => ['category1', 'category3'],
];

// Initialize an empty array to store the inverted map
$categories = [];

// Loop through each item in the input array
foreach ($items as $item => $itemCategories) {
// Loop through each category for the current item
foreach ($itemCategories as $category) {
// Check if the category already exists in the inverted map
if (!isset($categories[$category])) {
// If not, create a new key with an empty array as its value
$categories[$category] = [];
}
// Add the current item to the category's array
$categories[$category][] = $item;
}
}

// Output the inverted map
print_r($categories);

Output:
Array
(
[category1] => Array
(
[0] => item1
[1] => item3
)

[category2] => Array
(
[0] => item1
[1] => item2
)

[category3] => Array
(
[0] => item2
[1] => item3
)
)