Wordpress Add Custom Meta Box to Page

example.php

//Code for template file:
 global $post; 
 if ( get_post_meta($post->ID, 'active_page_showzipform', true )  ) :
   //Checkbox is checked... do somehting
 endif;

//Code for functions.php --- Begin Custom Code for Page Metabox
function active_add_meta_box() {

        add_meta_box(
            'active_metabox_pagesettings',      // id
            'Page Options',           // title
            'active_page_settings',      // callback function
            'page',                     // type of write screen
            'side',                     // context
            'low'                       // priority
        );
}
add_action( 'add_meta_boxes', 'active_add_meta_box' );

function active_page_settings(){
    global $post;
    $custom = get_post_custom($post->ID);
    $active_page_showzipform = $custom["active_page_showzipform"][0]; 
    ?>
    <input type="checkbox" name="active_page_showzipform" <?php if( $active_page_showzipform == true ) { ?>checked="checked"<?php } ?> />  Hide Zipcode Form
    <?php 

}


add_action('save_post', 'save_active_page_settings');

function save_active_page_settings($post_ID = 0) {
    $post_ID = (int) $post_ID;
    $post_type = get_post_type( $post_ID );
    $post_status = get_post_status( $post_ID );

    if ($post_type) {
    update_post_meta($post_ID, "active_page_showzipform", $_POST["active_page_showzipform"]);
    }
   return $post_ID;
}
//End Custom Code for Page Metabox