Description:
------------
The db2_conn_error() returns an empty value after a connection failure, although according to the documentation[1] it should be non-empty. Usually, an empty SQLSTATE is 00000.

[1] https://php.net/db2_conn_error

Test script:
---------------
$conn = db2_connect('badname', 'baduser', 'badpassword');

if (!$conn) {
    var_dump(db2_conn_error());
}


Expected result:
----------------
string(5) "08001"

Actual result:
--------------
string(5) "     "