Group 2d array data by a column and push the original row's index into the group's subarray

Question

I have an array like that:

array(
    [0] => array(
        'date' => '2017-12-20',
        'name' => 'test A',
        'kwa' => 'kwa1, kwa2'
    ),
    [1] => array(
        'date' => '2017-12-20',
        'name' => 'test B',
        'kwa' => ''
    ),
    [2] => array(
        'date' => '2017-12-21',
        'name' => 'test C',
        'kwa' => 'kwa1'
    ),
    [3] => array(
        'date' => '2017-12-22',
        'name' => 'test D',
        'kwa' => ''
    ),
    [4] => array(
        'date' => '2017-12-22',
        'name' => 'test E',
        'kwa' => ''
    ),
)

I want group all elements has the same day into a array. Something like that:

array(
    ['2017-12-20'] => array( '0', '1'),
    ['2017-12-21'] => array( '2' ),
    ['2017-12-22'] => array( '3', '4' ),
)

Answer 1

Here is your solution...

Input

<?php 
    $array = array(
        array(
            'date' => '2017-12-20',
            'name' => 'test A',
            'kwa' => 'kwa1, kwa2'
        ),array(
            'date' => '2017-12-20',
            'name' => 'test B',
            'kwa' => ''
        ),array(
            'date' => '2017-12-21',
            'name' => 'test C',
            'kwa' => 'kwa1'
        ),array(
            'date' => '2017-12-22',
            'name' => 'test D',
            'kwa' => ''
        ),array(
            'date' => '2017-12-22',
            'name' => 'test E',
            'kwa' => ''
        ),
    );

Solution

    $new = array();
    foreach($array as $r){
       $new[$r['date']][] = array('name'=>$r['name'],'kwa' => $r['kwa']); 
    }
    echo "<pre>";print_r($new);

?>

Output

    Array
(
    [2017-12-20] => Array
        (
            [0] => Array
                (
                    [name] => test A
                    [kwa] => kwa1, kwa2
                )

            [1] => Array
                (
                    [name] => test B
                    [kwa] => 
                )

        )

    [2017-12-21] => Array
        (
            [0] => Array
                (
                    [name] => test C
                    [kwa] => kwa1
                )

        )

    [2017-12-22] => Array
        (
            [0] => Array
                (
                    [name] => test D
                    [kwa] => 
                )

            [1] => Array
                (
                    [name] => test E
                    [kwa] => 
                )

        )

)