Returns the string error message explaining the error generated by the
last LDAP command for the given link_identifier.
While LDAP errno numbers are standardized, different libraries return
different or even localized textual error messages. Never check for a
specific error message text, but always use an error number to check.
Unless you lower your warning level in your php.ini sufficiently or prefix your LDAP commands with @ (at) characters to suppress warning output, the errors generated will also show up in your HTML output.