Add prefixes to WordPress post types when a theme is activated

gistfile1.php

<?php
 
/* Checks to see if new post type names (with prefixes) are being used. If not, then the old
 * post type names are converted as long as there aren't conflicting post type names that are
 * being registered by other plugins.
 *
 * @hook {action} after_setup_theme
 */
function fjarrett_prefix_post_types(){
	global $wpdb;

	$prefix = 'fjarrett_'; // Define the prefix you would like to use
	$post_types = array( 'acme', 'foo', 'bar' ); // Create an array of existing post type names you want to add the prefix to

	foreach ( $post_types as $post_type ) {

		// Check first to see if another plugin is registering a conflicting post type name
		if ( post_type_exists( $post_type ) ) {
			continue;
		}

		// Check to see if database entries exist for the prefixed post type
		$new_entries_exist = ( $wpdb->query( $wpdb->prepare( "SELECT * FROM " . $wpdb->posts . " WHERE post_type = %s", $prefix . $post_type ) ) ) ? true : false;

		// Move along if new entries exist
		if ( $new_entries_exist ) {
			continue;
		}

		// If we make it this far, check to see if database entries exist for the old post type
		$old_entries_exist = ( $wpdb->query( $wpdb->prepare( "SELECT * FROM " . $wpdb->posts . " WHERE post_type = %s", $post_type ) ) ) ? true : false;

		// Add the prefix to old entries
		if ( $old_entries_exist ) {

			$wpdb->query(
				$wpdb->prepare(
					'UPDATE ' . $wpdb->posts . ' SET post_type = %s WHERE post_type = %s',
					$prefix . $post_type,
					$post_type
				)
			);

			$wpdb->query(
				$wpdb->prepare(
					'UPDATE ' . $wpdb->posts . ' SET guid = replace( guid, "post_type = %s", "post_type = %s" )',
					$post_type,
					$prefix . $post_type
				)
			);

		}
	}
}
add_action( 'after_setup_theme', 'fjarrett_prefix_post_types' );

Nice dude. Looks like it should work just fine for converting existing post types. I'd like to implement this into EDD so that the post type is named something like "edd_download", instead of just "download".

I'll test it out soon.

Sadly, there is not a hook yet that fires only when themes are activated.

The after_setup_theme action is a little misleading in that it fires when WordPress sets up the current theme, not when an admin activates and/or configures the current theme. So, it's basically firing with every load of WP when the theme is active.

Someone first made a patch for this 3 years ago and it looks like it's finally being revisited now: http://core.trac.wordpress.org/ticket/7795

The changelog for register_activation_hook() looks depressing as well: http://codex.wordpress.org/Function_Reference/register_activation_hook#Changelog

Yeah, sad indeed. after_theme_setup is probably the best one to use for now.