entity-metadata-wrapper isset check.

entity-metadata-wrapper-isset.php

<?php
$field_collection_item = field_collection_item_load($id);
$item_wrapper = entity_metadata_wrapper('field_collection_item', $field_collection_item);

// this results in an error if the field_contrib_headshot field is empty
$headshot = $item_wrapper->field_contributor->field_contrib_headshot->value();

Solution:
// EntityStructureWrapper implements the __isset() function according the principe of Overloading.
$headshot = array();
if (isset($item_wrapper->field_contributor->field_contrib_headshot)) {
  $headshot = $item_wrapper->field_contributor->field_contrib_headshot->value();
}

// You can even directly call __isset method on wrapper.
print ($wrapper->__isset('field_property_sample') ? $wrapper->field_property_sample->value() : '';

       
// On nested field collections:
// When iterating over a list of field collections, and checking for a non-empty field collection
// nested within the first, isset() does not work. However, I found that checking:
foreach ($node_wrapper->field_fc_one AS $field_collection) {
  // Grab a nested field collection, properly wrapped.
  $nested_fc_wrapper = $field_collection->field_nested_fc;

  // isset() or $wrapper->__isset('') do not work here, but this does:
  if(nested_fc_wrapper->getIdentifier()) {
    // Do some stuff
  }
}