PHP平面数组一维高且空值

Question

我有这个数组$data：

Array
(
  [0] => Array
      (
          [0] => 1
      )

  [1] => Array
      (
      )

  [2] => Array
      (
      )

  [3] => Array
      (
          [0] => test@email.net
      )

)

每个数组中始终只有一个元素。那么，我如何将$data数组转换为此？我也需要空值：

Array
(
  [0] => 1
  [1] =>
  [2] =>
  [3] => test@email.net
)

Answer 1

使用array_map：

$arr = Array
(
  [0] => Array
      (
          [0] => 1
      )

  [1] => Array
      (
      )

  [2] => Array
      (
      )

  [3] => Array
      (
          [0] => test@email.net
      )

);

function flaten($n)
{
    if (isset($n[0])) {
       return $n[0];
    } else {
       return "";
    }
}

$resultArray = array_map(flaten, $arr);