View iterator_to_array for a recursive iterator to get a two-dimensional array

Question

when using iterators in PHP, you can use a function iterator_to_arrayto look at the array retrieval resulting from the iteration. For example, suppose you follow ArrayObject:

$array_object = new ArrayObject(array(
   array('1', '2', '3', '4'),
   array('5', '6', '7', '8'),
   array('9', '10', '11', '12'),
));

As you can see, its storage is a two-dimensional array.

We can FilterOperatoronly use for its first element (I know it would be better with LimitIterator, this is just an example):

class myFilterIterator extends FilterIterator
{
   public function accept()
   {
      return ($this->key() === 0);
   }
}

$filter_iterator = new myFilterIterator(new ArrayIterator($array_object));

Now if I do:

print_r(iterator_to_array($filter_iterator));

I get an array that I could get if I manually go through the statement:

Array ( [0] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 ) )

But now what if I want to work with RecursiveFilterIterator? Let's say I have:

class myRecursiveFilterIterator extends RecursiveFilterIterator
{
   public function accept()
   {
      return ($this->hasChildren() || $this->key() === 0);
   }
}

$recursive_filter_iterator = new myRecursiveFilterIterator(new RecursiveArrayIterator($array_object));

, 0 , . , :

foreach (new RecursiveIteratorIterator($recursive_filter_iterator) as $value) {
   print_r($value);
   echo '<br />';
}

:

1
5
9

array(array(1), array(5), array(9))?

:

print_r(iterator_to_array($recursive_filter_iterator));

print_r(iterator_to_array($recursive_filter_iterator->getInnerIterator()));

$it = new RecursiveIteratorIterator($recursive_filter_iterator);
print_r(iterator_to_array($it->getInnerIterator()));

:

Array ( [0] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 ) [1] => Array ( [0] => 5 [1] => 6 [2] => 7 [3] => 8 ) [2] => Array ( [0] => 9 [1] => 10 [2] => 11 [3] => 12 ) )

:

print_r(iterator_to_array(new RecursiveIteratorIterator($recursive_filter_iterator)));

:

Array ( [0] => 9 )

:

print_r(iterator_to_array(new RecursiveIteratorIterator($recursive_filter_iterator->getInnerIterator())));

, 0:

Array ( [0] => 9 [1] => 10 [2] => 11 [3] => 12 ) 

:

Array ( [0] => Array ( [0] => 1 ) [1] => Array ( [0] => 5 ) [2] => Array ( [0] => 9 ) ) 

, , , , , iterator_to_array . , -, PHP, .

.

Answer 1

, , RecursiveArrayIterator (note: ArrayObject ) iterator_to_array() , .

class FirstOnlyRecursiveArrayIterator extends ParentIterator {
    public function __construct(RecursiveArrayIterator $it) {
         parent::__construct($it);
    }
    public function current() {
        $children = parent::current();
        return array_slice($children, 0, 1);
    }
}

$array_it = new RecursiveArrayIterator(array(
    array('1', '2', '3', '4'),
    array('5', '6', '7', '8'),
    array('9', '10', '11', '12'),
));

$filter_iterator = new RecursiveIteratorIterator(
    new FirstOnlyRecursiveArrayIterator($array_it),
    RecursiveIteratorIterator::SELF_FIRST);
print_r(iterator_to_array($filter_iterator));

Answer 2

/ ? array_map() php, . , :

<?php
function get_first($foo)
{ 
    return array_slice($foo, 0, 1); //slice the array right after the first element
}

$array_object = new ArrayObject(array(
     array('1', '2', '3', '4'),
     array('5', '6', '7', '8'),
     array('9', '10', '11', '12'),
));

$new_array = array_map("get_first", $array_object->getArrayCopy());
print_r($new_array);
?>

:

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

    [1] => Array
        (
            [0] => 5
        )

    [2] => Array
        (
            [0] => 9
        )
)

, .

Answer 3

OK One simple way might be the following. It extends the ArrayIterator class and overrides the current () function to return a sparse array:

<?php
class FirstOnlyIterator extends ArrayIterator
{
    public function current()
    {
            $next = parent::current();
            return array_slice($next, 0, 1);
    }
}

$array_object = new ArrayObject(array(
     array('1', '2', '3', '4'),
     array('5', '6', '7', '8'),
     array('9', '10', '11', '12'),
));

$iterator = new FirstOnlyIterator($array_object);

print_r(iterator_to_array($iterator));
?>