当每个键都是一个字符串时，迭代PHP中的多维关联数组

I've got an array like:

$fruits = array(
  'citrus' => array(
    'fruit one' => 'orange',
    'fruit two' => 'lime',
  ),
  'melon' => array(
    'fruit one' => 'honeydew',
    'fruit two' => 'cantalope',
  ),
  'berry' => array(
    'fruit one' => 'raspberry',
    'fruit two' => 'strawberry',
  ),
  'apple' => array(
    'fruit one' => 'granny smith',
    'fruit two' => 'fuji',
  )

);

I want to be able to access slices of it, like echo $fruits[0]['fruit one']; so that I can create a for loop to get at specific groups of the array. By that I mean, I would ideally be able to do something like:

for($i = 0; $i <= 1; $i++)
  echo $fruit[$i]['fruit one'];

// Then some other code

for($i = 2; $i <= 3; $i++)
  echo $fruit[$i]['fruit one'];

Of course I can't do that since every key is a string. Is there a simple solution to this or did I just code this dumbly?

Edit: I made the array longer to fully demonstrate what I'm trying to do.

array_slice (docs) was made just for this.

For the first 2 fruit groups:

foreach(array_slice($fruits,0,2) as $fruitGroup) echo $fruitGroup['fruit one'];

For the next 2 fruit groups:

foreach(array_slice($fruits,2,2) as $fruitGroup) echo $fruitGroup['fruit one'];

Live demo

This has the benefit of simplicity (over Chrys' solution), and of not destroying the original keys from your array.

foreach ( $fruits AS $fruit ) {
  foreach ( $fruit AS $subFruit ) {
    // insert code here
  }
}

function replaceKeys(&$array)
{
    $ptr = null;
    foreach ($array as $values) {
        $ptr[] = $values;
    }
    $array = $ptr;
}

$fruits = array(
  'citrus' => array(
    'fruit one' => 'orange',
    'fruit two' => 'lime',
  ),
  'melon' => array(
    'fruit one' => 'honeydew',
    'fruit two' => 'cantalope',
  )
);


replaceKeys($fruits);

var_dump($fruits[0]['fruit one']);

//Output: orange