string ldap_error(int link_id);returns string error message.
This function 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 php3.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.
see also ldap_err2str() and ldap_errno().