Nerdlife

As promised here’s the example code from the meetup I gave last Monday. It’s fairly small, so I only describe what it does briefly in the top comment. Feel free to use it how you wish (though if you make a lot of money off of it you owe me a t-shirt):

Example 1: Erroring out on install

register_activation_hook(__FILE__, 'bostonwp_install_error');

if('error_scrape' == $_GET['action'] && basename($_SERVER['PHP_SELF']) == 'plugins.php') {
    echo '<pre>' . get_option('bostonwp_activate_error') . '</pre>';
    delete_option('bostonwp_activate_error');
    deactivate_plugins($_GET['plugin']);
    die();
}

function bostonwp_install_error($error = false) {
    if(!$error) {
        $error = 'Generic Error Occurred';
    }
    add_option('bostonwp_activate_error', $error);
    //trigger a fatal error
    trigger_error('', E_USER_ERROR);
}

Example 2: Updating your DB structure

// http://codex.wordpress.org/Creating_Tables_with_Plugins

define('BOSTONWP_DB_VERSION', '1.0');

register_activation_hook(__FILE__, 'bostonwp_install');

$wpdb->bostonwp = $wpdb->prefix . 'bostonwp';

function bostonwp_install() {
    global $wpdb;

    $installed_ver = get_option( 'bostonwp_db_version' );

    $sql = 'CREATE TABLE ' . $wpdb->bostonwp . ' (
        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)
        );';

    if($wpdb->get_var('show tables like "' . $wpdb->bostonwp . '"') != $wpdb->bostonwp) {
        require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
        dbDelta($sql);

        $welcome_name = 'Mr. WordPress';
        $welcome_text = 'Congratulations, you just completed the installation!';

        $insert = 'INSERT INTO ' . $wpdb->bostonwp .
            ' (time, name, text) ' .
            'VALUES (' . time() . ',"' . $wpdb->escape($welcome_name) . '","' . $wpdb->escape($welcome_text) . '")"';

        $results = $wpdb->query( $insert );

        add_option("bostonwp_db_version", BOSTONWP_DB_VERSION);
    }
    elseif( $installed_ver != BOSTONWP_DB_VERSION ) {
        require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
        dbDelta($sql);

        update_option( "bostonwp_db_version", BOSTONWP_DB_VERSION );
    }
}

Example 3: Adding admin menus

// http://codex.wordpress.org/Adding_Administration_Menus

add_action('admin_menu', 'bostonwp_menu');
function bostonwp_menu() {
    add_posts_page('My Page', 'My Page', 'manage_categories', 'bostonwp_page', 'bostonwp_dostuff');
}

function bostonwp_dostuff() {
?>
    <div class="wrap">
        <?php if(function_exists('screen_icon')) screen_icon(); ?>
        <h2>My Boston WP Page</h2>
    </div>
<?php
}

Example 4: Adding meta boxes to posts

// http://www.deluxeblogtips.com/2010/04/how-to-create-meta-box-wordpress-post.html

add_action('add_meta_boxes_post', 'bostonwp_box');
add_action('save_post', 'bostonwp_save');
add_action('delete_post', 'bostonwp_delete');

function bostonwp_box($post) {
    // http://codex.wordpress.org/Function_Reference/add_meta_box
    add_meta_box('bostonwp', __('Boston WP'), 'bostonwp_meta_box', 'post', 'side');
}

function bostonwp_meta_box() {
    global $post;
    $val = get_post_meta($post->ID, 'bostonwp', true);

    // Use nonce for verification
    echo '<input type="hidden" name="bostonwp_nonce" id="bostonwp_nonce" value="' . wp_create_nonce( plugin_basename(__FILE__) ) . '" />';

    // The actual fields for data entry
    echo '<input type="checkbox" name="bostonwp" value="1" ' . ($val ? ' checked="checked" ' : '') . ' />';
    echo '<label for="bostonwp">' . __('There Is Cake!') . '</label> ';
}

function bostonwp_save($id) {
    // verify nonce
    if ($_POST['action'] != 'inline-save' && !wp_verify_nonce($_POST['bostonwp_nonce'], plugin_basename(__FILE__))) {
        return $id;
    }

    // check autosave
    if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) {
        return $id;
    }

    update_post_meta($id, 'bostonwp', $_POST['bostonwp']);
}

function bostonwp_delete($id) {
    delete_post_meta($id, 'bostonwp');
}

Example 5: Adding columns to post list

add_filter('manage_posts_columns', 'bostonwp_posts_column');
add_action('manage_posts_custom_column', 'bostonwp_manage_column', 10, 2);

function bostonwp_posts_column($cols) {
    $cols['bostonwp'] = __('Boston WP');
    return $cols;
}

function bostonwp_manage_column($name, $id) {
    if($name != 'bostonwp') {
        return;
    }
    $cake = get_post_meta($id, 'bostonwp', true);
    if($cake) {
        echo 'There is cake!';
        $cake = 1;
    }
    else {
        echo 'The cake is a lie!';
        $cake = 0;
    }
    echo '<div id="inline_' . $id . '_bostonwp" class="hidden">' . $cake . '</div>';
}

Example 6: Expanding Quick Edit

add_action('quick_edit_custom_box', 'bostonwp_posts_custom_box', 10, 2);
add_action('admin_head-edit.php', 'bostonwp_add_script');

function bostonwp_posts_custom_box($col, $type) {
    if($col != 'bostonwp' || $type != 'post') {
        return;
    }
?>
<fieldset class="inline-edit-col-right"><div class="inline-edit-col">
    <div class="inline-edit-group">
        <label class="alignleft">
            <input type="checkbox" value="1" name="bostonwp" id="bostonwp_check">
            <span class="checkbox-title">This Post Has Cake</span>
        </label>
    </div>
</fieldset>
<?php
}

function bostonwp_add_script() {
?>
<script type="text/javascript">
jQuery(document).ready(function() {
    jQuery('a.editinline').live('click', function() {
        var id = inlineEditPost.getId(this);
        var val = parseInt(jQuery('#inline_' + id + '_bostonwp').text());
        jQuery('#bostonwp_check').attr('checked', !!val);
    });
});
</script>
<?php
}