ldap_unbind kills the link descriptor. So, if you want to rebind as another user, just bind again; don't unbind. Otherwise, you'll have to open up a new connection.
(PHP 4, PHP 5, PHP 7)
ldap_unbind — Unbind from LDAP directory
$link_identifier
) : boolUnbinds from the LDAP directory.
成功时返回 TRUE， 或者在失败时返回 FALSE。
ldap_unbind kills the link descriptor. So, if you want to rebind as another user, just bind again; don't unbind. Otherwise, you'll have to open up a new connection.