how to group array based on a value from within that array - php (laravel)

Question

I have a query from eloquent which I transform into an array. My goal is to group multiples of members into their respective group based on their group id, which each member holds. So essentially I would need a three dimensional array, with the first array holding the group ids, the second holding an array of each member, and the third holding that members information i.e.

Array(

    [1] => array(
                  array( [member_id] => 3
                         [type] => human
                         [group_id] => 1
                       ),
                  array( [member_id] => 4
                         [type] => alien
                         [group_id] => 1
                       ), 
                )
    [2] => array(
                  array( [member_id] => 9
                         [type] => human
                         [group_id] => 2
                       ),
                  array( [member_id] => 10
                         [type] => alien
                         [group_id] => 2
                       ), 
                )
)

I've tried a few things, the one that has gotten me closest to this goal is the following:

Sorting them by their group gives me a two dimensional array with the members being returned in ascending order, like so:

Array
(
    [0] => Array
        (
            [member_id] => 7
            [type] => human
            [group_id] => 1
        )

    [1] => Array
        (
            [customer_id] => 5
            [type] => alien
            [group_id] => 1
        )

    [2] => Array
        (
            [customer_id] => 8
            [type] => alien
            [group_id] => 2
        )
//there is no group #3, so next group is 4
    [3] => Array
        (
            [customer_id] => 3
            [type] => human
            [group_id] => 4
        )
)

But the keys are not based on group ids, they're just assigned by the function.

To make the first arrays keys actual group ids, I did the following:

        $sorted = array();
        $i=0;
        while($i <= count($members))
        {
            foreach($members as $member)
            {
                if($member['group_id'] == $i)
                {
                    $sorted[$i] = $member;
                }
            }
            echo $i;
            $i++;

        }

But this gave me only the first member for each group and not any more.

SOLUTION: I hope it's still okay to post the answer in my question, it just came to me while I was writing out this question lol...

I wasn't actually creating another array within $sorted[] in my if condition, so that's why it didn't append the other members, only one. I added a pair of brackets:

$sorted[$i][] = $member;

and it works :). Hope it helps someone in the future.

Barmar · Accepted Answer · 2014-01-30 00:52:19Z

1

$sorted = array();

foreach ($members as $member) {
    $groupid = $member['group_id'];
    if (isset($sorted[$groupid])) {
        $sorted[$groupid][] = $member;
    } else {
        $sorted[$groupid] = array($member);
    }
}

answered Jan 30, 2014 at 0:52

Barmar

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3 Comments

a7omiton Over a year ago

I get the same results as my own, but this is much cleaner. Is there anything wrong with my approach however (apart from too many conditional statements)? Thanks

Barmar Over a year ago

It's not "clean" to depend on PHP creating the empty arrays when you push onto them, although it works. It's like using .= to concatenate onto a string, but not initializing it to '' first. If you enable warnings, you'll probably get a notice about a reference to an undefined index.

a7omiton Over a year ago

Thanks for pointing that out, I wasn't aware of that. Will look into another solution sometime soon. I played a game of bridge out of excitement :D

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