DRUPAL 7 - get ID from entity

gistfile1.php

<?php

// Method 1: get both id key and id value. Verbose way.
$entity_wrapper = entity_metadata_wrapper($entity_type, $entity);
$pri = $entity_wrapper->entityKey('id');
$entity_id = $entity_wrapper->$pri->value();

// Method 2: get only id value. More succint way.
list($entity_id) = entity_extract_ids($entity_type, $entity);