Returns data about an individual field, given a field name.
$field_name: The name of the field to retrieve. $field_name can only refer to a non-deleted, active field. For deleted fields, use field_info_field_by_id(). To retrieve information about inactive fields, use field_read_fields().
The field array, as returned by field_read_fields(), with an additional element 'bundles', whose value is an array of all the bundles this field belongs to keyed by entity type. NULL if the field was not found.
function field_info_field($field_name) {
$cache = _field_info_field_cache();
return $cache
->getField($field_name);
}