prova una cosa del genere.

Codice PHP:

     $con= mysql_connect(host,username, password)or die ("Non riesco a connettermi al server ...  ");
    mysql_select_db('nome database', $con)or die (" Non trovo il database ...");

                     $query = "SELECT username FROM _reg_ WHERE username LIKE '$_POST[cerca%]'";

                        $select=mysql_query($query) or die("Query fallita");

                        $NumRow = mysql_num_rows($select);

                            if ($NumRow>0) // Il recordset NON è vuoto
                                {
                                      
                                               echo "<table>\n";
                                while ($linea = mysql_fetch_array($risultato, MYSQL_ASSOC)) 
                                    {
                                        echo "\t<tr>\n";
                                        foreach ($linea as $valore_colonna) 
                                        {
                                            echo "\t\t<td>$valore_colonna</td>\n";
                                        }
                                        echo "\t</tr>\n";
                                    }
                                    print "</table>\n";
                                
                                    /* Liberazione delle risorse del risultato */
                                    mysql_free_result($risultato);
                                
                                    /* Chiusura della connessione */
                                    mysql_close($connessione); 
                                                                            
                                 }
                            else
                                {
                                  print("Nessun record trovato); 
                                                                                       
                                } 
cosi almeno controlli se ci sono risultati e se ci sono gli stampi a video altrimenti stampi a video "nessun record trovato"