Question

I have the following array:

array(2) {
  [0] => array(4) {
    ["presentation_id"] => int(143)
    ["user_id"] => int(2)
    ["session_id"] => int(46)
    ["submission_id"] => int(190)
}
[1] => array(4) {
    ["presentation_id"] => int(144)
    ["user_id"] => int(2)
    ["session_id"] => int(46)
    ["submission_id"] => int(190)
}

What I want is to have an array consisting of just certain keys of this array, for example:

array(2) {
  [0] => array(4) {
    ["presentation_id"] => int(143)
    ["user_id"] => int(2)
}
[1] => array(4) {
    ["presentation_id"] => int(144)
    ["user_id"] => int(2)
}

Any ideas?

Answer 1

$array = array_map(function ($arr) {
    return array_intersect_key($arr, array_flip(array('presentation_id', 'user_id')));
}, $array);

Important to note that this syntax requires PHP 5.3+.

For other versions:

foreach ($array as &$arr) {
    $arr = array_intersect_key($arr, array_flip(array('presentation_id', 'user_id')));
}

I’d suggest this over unsetting unwanted keys (as suggested by others) if you definitely want to restrict the array to certain elements. If you add more elements to the array in the future you won’t need to update this code, but you’d have to unset more elements that you may not want.