PHP - Manual: yaz_errno (官方文档)
(PHP 4 >= 4.0.1, PECL yaz >= 0.9.0)
yaz_errno — Returns error number
$id) : int
Returns an error number for the server (last request) identified by
yaz_errno() should be called after network activity for each server - (after yaz_wait() returns) to determine the success or failure of the last operation (e.g. search).
The connection resource returned by yaz_connect().
Returns an error code. The error code is either a Z39.50 diagnostic code (usually a Bib-1 diagnostic) or a client side error code which is generated by PHP/YAZ itself, such as "Connect failed", "Init Rejected", etc.