Is there a PHP Array Group By function?

$arr1 = array('a' => '1', 'b' => 'blah', 'c' => 'whatever...',
              'aa' => '2', 'bb' => 'lbha', 'cc' => 'everwhat...', 'dd' => 'bingo',
              'aaa' => '3', 'bbb' => 'halb', 'ccc' => 'revetahw...');

In the array I have three different index lengths a,b and c are all 1 in length. aa,bb,cc and dd are all 2 in length. And aaa,bbb and ccc are all 3 in length.

What I'm trying to do is find the index (group by len开发者_开发知识库gth) with the most elements and the greatest length.

so I would use aa,bb,cc,dd as they have 4 elements, this would return the index length of 2.

I want to know how I can get the 2?

Here is what I'm trying but it's not working

foreach($arr1 as $key => $data) {
   $index_length_arr[strlen($key)] = $index_length_arr[$key] + 1;
}

Results:

Array
(
    [1] => 1
    [2] => 1
    [3] => 1
)

Expected Output:

Array
(
    [1] => 3
    [2] => 4
    [3] => 3
)

Then I could see that index (with the length of 2) had the most elements:

'aa' => '2', 'bb' => 'lbha', 'cc' => 'everwhat...', 'dd' => 'bingo',

$array = array_count_values(array_map('strlen',array_keys($arr1)));

Should give ya what ya want.

Edit:

Your original code was fine except you have to change the = .... to $index_length_arr[strlen($key)]

You were using two different keys.

I'd recommend creating your own (or using a library that already does it). It'd be something like this (did not test it):

function groupBy($array, $function)
{
    $dictionary = [];
    if ($array) {
        foreach ($array as $item) {
            $dictionary[$function($item)][] = $item;
        }
    }
    return $dictionary;
}

Using it like this:

$usersByAge = groupBy($users, function ($age) { return $user->age; } );

I would highly recommend using lstrojny's functional-php https://github.com/lstrojny/functional-php which includes a group() function along with a host of other useful functional programming concepts.

$arr1 = array('a' => '1', 'b' => 'blah', 'c' => 'whatever...',
              'aa' => '2', 'bb' => 'lbha', 'cc' => 'everwhat...', 'dd' => 'bingo',
              'aaa' => '3', 'bbb' => 'halb', 'ccc' => 'revetahw...');


$tmpArray = array();

foreach ($arr1 AS $key => $val) {
    if (empty($tmpArray)) {
            $tmpArray[strlen($key)] = 0;
    }
    $tmpArray[strlen($key)]++;
}

print_r($tmpArray);

Gets you your expected result.