This tip is more for WordPress theme and plugin developers. I’ve been working on a client project that required MySQL transactions, as I needed to perform multiple deletions on multiple tables, where the data was interdependent. Since I was writing a WordPress plugin, I wanted a way of doing a MySQL database transaction, using the WordPress database object $wpdb.

When you create a connection to a MySQL database, you end up with a connection handle. This is essentially a way of communicating with the database down the same pipe. When you render a page in WordPress (front end or admin area), the $wpdb database object has already been initialised and opened up a connection to the database. Therefore we can recycle this database connection for our own needs.

The $wpdb object saves the database handle as $wpdb->dbh (dbh = Database Handle). Therefore we just use $wpdb->dbh in place of our normal database handle that we’d otherwise use in PHP.

Code Example

<?php
global $wpdb;
 
// @ prefix used to suppress errors, but you should do your own
// error checking by checking return values from each mysql_query()
 
// Start Transaction
@mysql_query("BEGIN", $wpdb->dbh);
 
// Do some expensive/related queries here
$wpdb->query("DELETE FROM table WHERE form_id = '1' ");
$wpdb->query("DELETE FROM data WHERE form_id = '1' ");
 
if ($error) {
    // Error occured, don't save any changes
    @mysql_query("ROLLBACK", $wpdb->dbh);
} else {
   // All ok, save the changes
   @mysql_query("COMMIT", $wpdb->dbh);
}
 
?>

Based on this, you can do your usual PHP and WordPress magic to do what you need.

Portfolio In Action

After lots of work, I’ve publically released my first wordpress plugin called WP Portfolio, which is now available directly from the WordPress Plugin Database.

The WP Portfolio plugin allows you to create a list of the websites you own or developed, which are then published on a page on your website. The plugin automatically generates thumbnails of each of your sites for you too. An example of the plugin in action is on my own portfolio page.

Portfolio Admin Area

The WP portfolio plugin is ideal if you want to advertise all of the sites you work on, but where you don’t want to spend ages creating thumbnails. You have complete control over the HTML and CSS to render the thumbnails, but a default layout is provided to get you going. The thumbnails are generated using a free account on Shrink The Web.

Here’s summary of what you can do with the plugin:

• Create a list of your websites with a name, URL and description
• Group similar websites together, with a title and description for that group.
• Automatically generate thumbnails in a small (120 x 90), large (200 x 150) or extra large size (320 x 240).
• Adjust the number of days to cache the thumbnail on your site (to reduce load times)
• Customise the HTML and CSS used to render the site and group fields.

Any feedback, suggestions and ideas are greatly welcomed.