迭代数组并创建多维

Question

For simplicity I have an array:

 Array (
[0] => Array
    (
        [content] => Item One
        [type] => Breakfast
    )
[1] => Array
    (
        [content] => Item Two
        [type] => Breakfast
    )
[2] => Array
    (
        [content] => Item One
        [type] => Lunch
    )
[3] => Array
    (
        [content] => Item One
        [type] => Dinner
    )
 )

What is the most efficient way to create a new multidimensional array where it would combine on matching key "type"? Like below. Current trying in a foreach. Are there any built in functions for this?

 Array (
[0] => Array
    (
        [content] => Item One
        [type] => Breakfast
    ),
    (
        [content] => Item Two
        [type] => Breakfast
    )
[1] => Array
    (
        [content] => Item One
        [type] => Lunch
    ),
[2] => Array
    (
        [content] => Item One
        [type] => Dinner
    )
 )

Answer 1

You have to iterate through the input array and create a new output array. Take a look at this simple example:

<?php
$input = [
    [
        'content' => 'Item One',
        'type' => 'Breakfast',
    ],
    [
        'content' => 'Item Two',
        'type' => 'Breakfast',
    ],
    [
        'content' => 'Item Three',
        'type' => 'Lunch',
    ],
    [
        'content' => 'Item Four',
        'type' => 'Dinner',
    ]
];
$output = [];

array_walk(
    $input,
    function($element) use (&$output) {
        $output[$element['type']][] = $element;
    }
);
print_r($output);

The output of above obviously is:

Array
(
    [Breakfast] => Array
        (
            [0] => Array
                (
                    [content] => Item One
                    [type] => Breakfast
                )

            [1] => Array
                (
                    [content] => Item Two
                    [type] => Breakfast
                )

        )

    [Lunch] => Array
        (
            [0] => Array
                (
                    [content] => Item Three
                    [type] => Lunch
                )

        )

    [Dinner] => Array
        (
            [0] => Array
                (
                    [content] => Item Four
                    [type] => Dinner
                )

        )

)

Of course you can place whatever element and structure you want inside the created array. For this example I just accepted the original elements, since that is irrelevant for demonstrating how to easily iterate through the array.

If you insist on a numeric key sequence in the output array, then you can simply use print_r(array_values($output)); instead of print_r($output)...