获取多维数组上特定键的值

Question

Array([130] => Array
       (
        [0] => Array
            (
                [first_name] => John
                [last_name] => Smith
            )
        [1] => Array
            (
                [first_name] => Jane
                [last_name] => Doe
            )
    [123] => Array
      (
        [0] => Array
            (
                [first_name] => Ann
                [last_name] => Green
            )
        [1] => Array
            (
                [first_name] => Thor
                [last_name] => Grey
            )
        )

How to make array like this

   Array(
         [130] => Array
          (
            [first_name] => "John, Jane"
         [123] => Array
         (
           [first_name] => "Ann, Thor"
         )

Answer 1

Here's a quick and simple solution using a foreach() and a variable by reference:

foreach($your_array as &$current) {
    $current = array(
        'first_name' => $current[0]['first_name'] . ', ' . $current[1]['first_name']
    );
}

But assuming that you might have multiple people in your sub-arrays rather than just two, here's a better solution:

foreach($your_array as &$current) {
    $to_append = array(); // use a temporary array
    foreach($current as $sub_array) {
        $to_append[] = $sub_array['first_name']; // add each first name to temp
    }
    // overwrite current main array iteration with imploded temporary array
    $current = array('first_name' => implode(', ', $to_append));
}

--

Update

Here's another solution that doesn't use a foreach(), instead using a combination of array_walk() and array_map() with variables by reference:

array_walk($your_array, function(&$array_branch) {
    $names = array_map(function($a){
        return $a['first_name']; // return all the first names
    }, $array_branch);

    // combine the first names together
    $array_branch = array('first_name' => implode(', ', $names)); 
});

$array_branch represents each array inside your main array (keys 130 and 123) and is passed by reference so its value is overwritten each time