(PHP 4 >= 4.0.1, PECL)
This function sets the element set name for retrieval.
Call this function before yaz_search() or yaz_present() to specify the element set name for records to be retrieved.
注: If this function seems effectless, see the description of the piggybacking option in yaz_connect().
The connection resource returned by yaz_connect().
Most servers support F (for full records) and B (for brief records).
如果成功则返回 TRUE,失败则返回 FALSE。