Написание плагина. Не создаётся БД.

Пишу плагин под сапу, с БД&API имею дело первый раз. Объясните почему данный код не создаёт в БД таблицу с префиксом wp_madsape.

<?php
/*
Plugin Name: Mad_Sape
Plugin URI: http://страница_с_описанием_плагина_и_его_обновлений
Description: Установка кода Sape.
Version: 1.0
Author: Yuriy 'Mad_Man' Lagodich
Author URI: http://d-o-b.ru/
*/
/*  Copyright 2010 Lagodich Yuriy Vladimirovich (email: admin@m7team.ru)

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

global $jal_db_version;
$jal_db_version = "1.0";
register_activation_hook(__FILE__,'jal_install');

function jal_install () {
   global $wpdb;
   global $jal_db_version;

   $table_name = $wpdb->prefix . "madsape";
   if($wpdb->get_var("show tables like '$table_name'") != $table_name) {

      $sql = "CREATE TABLE " . $table_name . " (
	  id mediumint(9) NOT NULL AUTO_INCREMENT,
	  time bigint(11) DEFAULT '0' NOT NULL,
	  name tinytext NOT NULL,
	  text text NOT NULL,
	  url VARCHAR(55) NOT NULL,
	  UNIQUE KEY id (id)
	);";
	     require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
      dbDelta($sql);

      $rows_affected = $wpdb->insert( $table_name, array( 'time' => current_time('mysql'), 'name' => $welcome_name, 'text' => $welcome_text ) );

      add_option("jal_db_version", $jal_db_version);
}
}

add_action('admin_menu', 'sape_menu');

function sape_menu() {
    add_submenu_page('options-general.php'
                     , 'Mad_Sape'
                     , 'Mad_Sape'
                     , 'edit_plugins'
                     , __FILE__
                     , 'callme');
add_action('admin_menu', 'callme');
}
function callme() {
include 'wp_area.php';
add_action('admin_menu', 'footer');
}
function footer() {
add_action('wp_footer', 'sape_code');
}
function sape_code() {
include 'sape.php';
}
?>