Registro user

[ale_dla]

Hola a todos!
Tengo un código básico para el registro de un user.
Funciona bien la validación, el problema es que quiero validar si las 2 contraseñas ingresas coinciden sino muestra un msj de error.
Código PHP:

Código PHP:

  $error = "";
 if(!empty($_POST['username']) || (!empty($_POST['pass1'])) || (!empty($_POST['pass2'])) ){
                            $username = $_POST['username'];
                            $username = mysql_real_escape_string($username);
                            
                            $pass1 = $_POST['pass1'];
                            $pass2 = $_POST['pass2'];
                            if ($pass1 != $pass2) 
                            {
                                $error = "<div class=\"box red\">
                                        <p>Las contrase&ntilde;as no coinciden..</p>
                                    </div>";
                            }
                            else
                            {
                                $pass1 = mysql_real_escape_string($pass1);
                                $pass = md5($pass1); 
                            
                                $sql = "INSERT INTO admin (username,password) 
                                VALUES ('$username','$pass')";
                                $query = mysql_query($sql) or die(mysql_error());
                                header("Location:index.php?register_admin");
                            }
                        }
                        else
                        {
                            $error = "<div class=\"box red\">
                                        <p>Escribe nombre de usuario.</p>
                                        <p>Escribe contrase&ntilde;a.</p>
                                        <p>Repite la contrase&ntilde;a.</p>
                                    </div>";
                        }

$body .= '<div class="admin_content">
                                    <form action="" method="post" enctype="multipart/form-data">
                                    '.$error.'
                                    <div class="info">
                                    <p>
                                    <label for="username">Usuario</label> <input type="text" name="username" id="username"/>
                                    <span id="status"></span>
                                    </p>
                                    <p>
                                    <label for="pass">Contrase&ntilde;a</label> <input type="password" name="pass" />
                                    </p>
                                    <p>
                                    <label for="pass2">Repite contrase&ntilde;a</label> <input type="password" name="pass2" />
                                    </p>
                                    <p>
                                    <input type="submit" value="Registrar" class="submit" />
                                    </p>
                                    </div>
                                    </form>
                                    </div>';  
   

Quien pueda ayudarme se los agradezco!
Muchas gracias.
Saludos!