In Magento, if we are required to check the items of Bundle product for some purpose, then we can do it by following way:

For the same purpose lets check the below code:

< ?php

 $product = new Mage_Catalog_Model_Product();  
 $product->load($BUNDLED_PRODUCT_ID);


 $selectionCollection = $product->getTypeInstance(true)->getSelectionsCollection(
  $product->getTypeInstance(true)->getOptionsIds($product), $product
 );

 $items = array();
 foreach($selectionCollection as $option)
 {
  $items[] = $option->product_id;
 }

 print_r($items);

?>

In the above code lets see what we have done, first of all we have loaded the product to the $product. the next step is to get the collection i.e., the array of the Bundle product.

To do so we have used a Magento function getSelectionsCollection() method and passed the product Type Instance
and option Ids. Now, as we have assigned the collection to the array $selectionCollection, the next step is to extract the bundle items ID.

In the foreach loop the $selectionCollection is passed in array place and extracted the Bundle items Ids through $option->product_id and assigned to $items[] array.

Finally we have the Bundle Product's Item Ids in the array $items[]. In the final step we have printed the $items[] array to display the ids.

That's how we can get the item from the Bundle product to perform any operations on them.