Description
string 
pg_last_error ( [resource connection] )
   pg_last_error() returns the last error message
   for a given connection. 
  
   Error messages may be overwritten by internal PostgreSQL (libpq)
   function calls. It may not return an appropriate error message if
   multiple errors occur inside a PostgreSQL module function.
  
   Use pg_result_error(), pg_result_error_field(),
   pg_result_status() and
   pg_connection_status() for better error handling.
  
Note: 
    This function used to be called pg_errormessage().