What is an easy way to put an element in the middle of a PHP array?

Question

Say you have a 10 element indexed array and you want to place an element somewhere in the middle (say index 3). Then I want to have the rest of the array shift and thus be 11 elements long. Is there an easy way to do this?

I am surprised there is no put() function or something.

I know it would be easy enough to do this with a combination of array_splice and array_merge but I was just wondering if there an easier way.

Answer 1

array_splice() does this

$input = array("red", "green", "blue", "yellow");
array_splice($input, 3, 0, "purple");
// $input is now array("red", "green", "blue", "purple", "yellow");

Answer 2

Unfortunately your best bet is what you described in your post.

Answer 3

No PHP function can currently handle this. It is not too difficult to whip up your own, however:

function array_insert(&$array, $insert, $position) {
    $c = count($array);
    $slice = array_merge($insert, array_slice($array, $position));
    array_splice($array, $position, $c, $slice);
}

$array = array('a','b','d','e');
print_r($array);
array_insert($array, array('c'), 2);
print_r($array);

Will result in:

Array
(
    [0] => a
    [1] => b
    [2] => d
    [3] => e
)
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => e
)

You can probably add checks if the position is bigger than the array, the insert is not an array, etc.

Answer 4

If you use array_splice(), PHP will still have to copy half the array to do the insert, which will be a performance hit for large array sizes. Maybe you should be using a list or tree datastructure instead?

The only time I've ever needed to insert into the middle of an array was when I was doing some operation that's substantially similar to insertion sort. Maybe you want to store the items unsorted in an array, and then sort them once you've added them all?