Sets retval to the
value of the specified option. 成功回傳TRUE失敗回傳FALSE。
The parameter option
can be one of: LDAP_OPT_DEREF, LDAP_OPT_SIZELIMIT,
LDAP_OPT_TIMELIMIT, LDAP_OPT_PROTOCOL_VERSION,
LDAP_OPT_ERROR_NUMBER, LDAP_OPT_REFERRALS, LDAP_OPT_RESTART,
LDAP_OPT_HOST_NAME, LDAP_OPT_ERROR_STRING,
LDAP_OPT_MATCHED_DN. These are described in draft-ietf-ldapext-ldap-c-api-xx.txt
注: This function is only available when using OpenLDAP 2.x.x OR Netscape Directory SDK x.x, and was added in PHP 4.0.4
See also ldap_set_option().