PHP - 访问数组中的数据

Can't seem to work out how to access data within an array that has other arrays within it.

My array looks like:

Array
(
    [0] => Array
        (
            [_id] => 28
            [serv_image] => 
            [serv_name] => My Service
            [slug] => my-service
            [is_featured] => 
            [_blocks] => Array
                (
                    [0] => Array
                        (
                            [anchor_heading] => Mats Heading
                            [_block_type] => anchorHeading
                            [_block_id] => pe8t69
                            [_block_index] => 0
                        )

                    [1] => Array
                        (
                            [anchor_heading] => Another anchored heading
                            [_block_type] => anchorHeading
                            [_block_id] => pea49u
                            [_block_index] => 1
                        )

                )

            [_page] => *
            [_pageID] => 1
            [_sortvalue] => 1003
        )

)

So far I've tried this without success:

foreach($services as $service) {
    print_r($service['_blocks']['anchor_heading']);
}

This results in undefined index on anchor_heading.

UPDATE

I will have an unknown amount of these that I need to group together into a variable. How can I ensure I'm grabbing them all, no matter how many other times it's been entered?

You might use 2 times a foreach and echo the value of anchor_heading:

foreach($services as $service) {
    foreach ($service["_blocks"] as $block) {
        echo $block["anchor_heading"];
    }
}

You have an array for each _block .. so you need an indexed access .. (or an inner iteration)

foreach($services as $service) {
  print_r($service['_blocks'][0]['anchor_heading']);
  print_r($service['_blocks'][1]['anchor_heading']);
}

(or an inner iteration)

  foreach($services as $service) {
      $blocks  = $service['_blocks'];
      foreach( $blocks as $block) {
          print_r($block['anchor_heading']);

      }
  }

You can use the following to access the data within your array in a for loop:

print($service['_blocks'][0]['anchor_heading']);