I have a function called `createCost`, and inside that function, I have an `array_map` that takes in an array and a function called `checkDescription` that's inside that `createCost`. Below is an example:

```
public function createCost{

  $cost_example = array();
  function checkDescription($array_item)
  {
    return $array_item;
  }

  $array_mapped = array_map('checkDescription', $cost_example);
}

```

When I run this I get a 

```
array_map() expects parameter 1 to be a valid callback, function 'checkDescription' not found or invalid function name

```

Which to my understanding is that it looked for the function `checkDescription` outside that `createCost` but how can I call `checkDescription` from inside?