从基于公共ID的多维数组中获取多个数组

Question

I have one large array and I want to group this into other arrays based on a common ID so that I can use array_splice to get only the first and last occurrence of that ID.

array( 
    [0] => array(id => 34, name = "walter"),
    [1] => array(id => 25, name = "walter jr"),
    [2] => array(id => 34, name = "saul"),
    [3] => array(id => 25, name = "jesse"),
    [4] => array(id => 25, name = "todd")
   )

What I want to end up with is something like this.

array( 
    [0] => array(
                 id => 34, name = "walter",
                 id => 34, name = "saul"
                ),

    [1] => array(
                 id => 25, name = "walter jr",
                 id => 25, name = "jesse",
                 id => 25, name = "todd"
                 )
     )

I'm having a really hard time trying to wrap my head around how to accomplish this and have searched all over. I've found some solutions using array_unique and array_diff but i'm never able to get the result i'm looking for.

Answer 1

You can use array_reduce to group array elements, see below:

$data = array(
  0 => array('id' => 34, 'name' => "walter"),
  1 => array('id' => 25, 'name' => "walter jr"),
  2 => array('id' => 34, 'name' => "saul"),
  3 => array('id' => 25, 'name' => "jesse"),
  4 => array('id' => 25, 'name' => "todd")
);

$result = array_reduce($data, function ($result, $item){
  if (!isset($result[$item['id']])) {
        $result[$item['id']] = array();
  }
  $result[$item['id']][] = $item;
  return $result;
}, array());
print_r(array_values($result));

and result is:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [id] => 34
                    [name] => walter
                )

            [1] => Array
                (
                    [id] => 34
                    [name] => saul
                )

        )

    [1] => Array
        (
            [0] => Array
                (
                    [id] => 25
                    [name] => walter jr
                )

            [1] => Array
                (
                    [id] => 25
                    [name] => jesse
                )

            [2] => Array
                (
                    [id] => 25
                    [name] => todd
                )

        )

)