从PHP迭代器返回多个项目

Is there a way with a PHP Iterator object to sometimes return multiple items from a single item?

For example, suppose I have an array:

$a = ['1','2','3','double 6','4'];

and I want to have an Iterator object that takes this and produces the following items:

• 1
• 2
• 3
• 6
• 6
• 4

You have to make of definite array for such string like

"double"=>2,"triple"=>3,"quadruple"=>4, "quintuple"=>5

<?php
  $str = ["double"=>2,"triple"=>3,"quadruple"=>4, "quintuple"=>5];
  $a = ['1','2','3','double 6','4'];
  foreach($a as $key=>$val){
    $val = explode(" ",$val);
    if(count($val) > 1){
      $a[$key] = $val[1];
      for($i=1;$i<$str[$val[0]];$i++){
        $a[] = $val[1];
      }
    }
  }
  sort($a);
  print_r($a);
?>

Live Demo

One way that has occurred to me since posting the question is to use a Generator instead:

function my_iteration($data) { foreach ($data as $item) { if (IS DOUBLE) { yield $item; yield $item; } else { yield $item; } } }

This looks like flattening the array. If you are not worried about the memory you can use an initial array in the following form:

$array = ['1', '2', '3', ['6', '6'], '4'];

And then use RecursiveIteratorIterator:

function flatArray1($array): iterator
{
    $iterator = new RecursiveIteratorIterator(new RecursiveArrayIterator($array));
    foreach ($iterator as $item) {
        yield $item;   
    }
}

print_r(iterator_to_array(flatArray1($array)));

If you want to use less memory you can use a kind of zipped version of an initial array:

$array = ['1', '2', '3', [2, '6'], '4'];

function flatArray2($array): iterator
{
    foreach ($array as $item) {
        if (is_array($item)) {
            [$count, $item] = $item;

            while ($count) {
                yield $item;

                $count -= 1;
            }

            continue;
        }

        yield $item;
    }
}

print_r(iterator_to_array(flatArray2($array)));

Here is the demo.