Question

I am terrible with manipulating arrays…given this structure I want to remove the top level array and merge all subsets into one flat array:

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [0] => hey.com
                )

            [1] => Array
                (
                    [0] => you.com
                )
        )
    [1] => Array
        (
            [0] => Array
                (
                    [0] => this.com
                )

            [1] => Array
                (
                    [0] => rocks.com
                )
        )
)

to desired structure:

Array
    (
        [0] => hey.com
        [1] => you.com
        [2] => this.com
        [3] => rocks.com
    )

Speed is essential – we will be dealing with hundreds of thousands of results

Answer 1

You can use RecursiveArrayIterator

$it = new RecursiveIteratorIterator(new RecursiveArrayIterator($data));
$list = iterator_to_array($it,false);
var_dump($list);

Output

array (size=4)
  0 => string 'hey.com' (length=7)
  1 => string 'you.com' (length=7)
  2 => string 'this.com' (length=8)
  3 => string 'rocks.com' (length=9)

See Simple Demo