Web and Mobile Apps Dev

After almost 3 hours of researches and trials, I finally finished the first one-page WordPress plugin called “identi.ca reminder”. As the name suggests, it’s used for reminding me to post an update whenever I added or updated a blog post. Since identi.ca also posts updates automatically to Twitter and Facebook, I only need to update the status for my identi.ca account. And because the lack of the good identi.ca-related WordPress plugins, I decided to manually update the status once a blog post is added or updated.

This was the first time I began to learn WordPress plugin. Thanks to the detailed documentation on the WordPress Codex wiki, I was able to learn and create the plugin at the same time. Here is the whole source code for my basic plugin (also includes very detailed comments):

<?php
/*
Plugin Name: identi.ca Reminder
Plugin URI: http://wordpress.org/#
Description: This is my first plugin simply remind you to post an update on identi.ca after a blog post is published/updated
Author: Robby Chen
Version: 1
Author URI: http://blog2.robbychen.com/
*/

    // Function to output the reminder
function reminderID($messages) {
    $reminder = array();    // An empty array to store the duplication of the messages array
    $others = array();      // An empty array to store the arrays for post types other than messages['post']
    foreach ($messages['post'] as $num=>$message) {
        $message .= "<br /><br />Make sure to update your <a href='http://www.identi.ca/robbychen' target='_blank'>identi.ca</a> status.";
        if ($num == 0) {
            $message = "";  // The first element in the messages['post'] array is always empty
        }
        array_push($reminder, $message);    // Insert/copy the modified message value to the last element of reminder array
    }
    $reminder = array("post"=>$reminder);   // Apply the post key to the first dimension of messages array
    foreach ($messages as $type=>$message) {
        if ($type == "post") {  // Skip the post key since it is already defined
            continue;
        }
        $others[$type] = $message; // Since message is an array, this statement forms 2D array
    }
    $reminder = array_merge($reminder, $others);    // Merge the arrays in the others array with reminder array in order to form an appropriate format for messages array
    return $reminder;
}
    // Print the above message when a blog post is submitted or updated
add_filter("post_updated_messages", "reminderID");
?>

Note that when I wrote and tested this plugin, the “messages['post']” array cannot be changed partially. The only way I can change the value is to copy the modified value to a new array, then make the structure of the new array the same as messages’. For instance, I tried to do the following in the code above:

$messages = array('post'=>array(), 'page'=>array(), 'custom_types'=>array(), ...);
$reminder = array('post'=>array(), 'page'=>array(), 'custom_types'=>array(), ...);

It seems that without this format, the add_filter function would not be executed. As the above example shows, it just applies to the “post” post type, although I have not tested it with custom post type yet.

You can download the source file here.

Below are the resources I used to help me for creating this plugin:

• WordPress plugin API wiki: http://codex.wordpress.org/Plugin_API
• Hello Dolly plugin (for template purpose): http://wordpress.org/extend/plugins/hello-dolly/
• add_filter wiki: http://codex.wordpress.org/Function_Reference/add_filter
• post_updated_messages usage: http://wordpress.org/support/topic/add-text-to-massage-box