1. building pluggable plugins
@brandondove #plugplug #wcla

2. pluggable plugins are...
• also known as core plugins
• built by a team of developers rather than a single developer
• more secure
• less buggy
• easier to customize than a traditional plugin
• supported by original developers
• ever changing

3. their importance...
• plugin repository is a mess
• instill confidence in users
• developers can’t know

4. OOP concept: inheritance
• allows developers to reuse common pieces of code.
• class structures help you play nice
• helps keep code maintainable

5. sub
base sub
sub
OOP diagram

6. cars share basic functionality: driving, steering, lights on/off

7. class subClass extends baseClass {
protected function publish( $obj ) {
// method must be defined
wp_insert_post( $obj );
}
abstract class baseClass { protected function update( $obj ) {
// method must be defined
abstract protected function publish( $obj ); wp_update_post( $obj );
abstract protected function update( $obj ); }
abstract protected function delete( $obj );
protected function delete( $obj ) {
public function get_post( $id ) { // method must be defined
$post = get_posts( 'p='.$id ); wp_delete_post( $obj );
return $post; }
}
} }
$sub = new subClass;
$my_post = $sub->get_post( 1 );
$my_post[0]->post_content = 'Some new content';
$sub->update( $my_post[0] );
$sub->delete( 1 );
PHP5 OOP implementation

8. WordPress concepts: actions & filters
• actions allow themes and plugins to execute code
• filters allow themes and plugins to modify output
• these are what make WordPress REALLY awesome

9. WordPress actions
do_action( 'non_clashing_action_name', $args );
add_action( 'non_clashing_action_name', 'my_hooking_function', (int) priority, (int) arguments );
function my_hooking_function( $args ) {
// execute some code here
}

10. class subClass extends baseClass {
function __construct() {
add_action( 'base_class_publish',
array( &$this, 'notify_me' ), 1, 1 );
}
protected function publish( $obj ) {
do_action( 'base_class_publish', $obj );
wp_insert_post( $obj );
}
abstract class baseClass { protected function notify_me( $obj ) {
wp_mail(
abstract protected function publish( $obj ); 'brandon@pixeljar.net',
abstract protected function update( $obj ); 'post published',
abstract protected function delete( $obj ); print_r( $obj, true )
);
public function get_post( $id ) { }
$post = get_posts( 'p='.$id );
return $post; protected function update( $obj ) {}
} protected function delete( $obj ) {}
} }
$sub = new subClass;
$my_post = array(
'post_title' => 'My post',
'post_content' => 'This is my post',
'post_status' => 'publish',
'post_author' => 1,
'post_category' => array( 8, 39 ) );
$sub->publish( $my_post );
PHP5 OOP + WordPress actions implementation

11. WordPress filters
echo apply_filters( 'non_clashing_filter_name', $args );
add_filter( 'non_clashing_filter_name', 'my_filtering_function', (int) priority, (int) arguments );
function my_filtering_function( $args ) {
return htmlentities( $args );
}

12. class subClass extends baseClass {
function __construct() {
add_filter( 'base_class_publish',
array( &$this, 'i_wrote_this' ), 1, 1 );
}
protected function publish( $obj ) {
$obj = apply_filters(
'base_class_publish', $obj );
abstract class baseClass { wp_insert_post( $obj );
}
abstract protected function publish( $obj );
abstract protected function update( $obj ); protected function i_wrote_this( $obj ) {
abstract protected function delete( $obj ); $obj['post_author'] = 2;
return $obj;
public function get_post( $id ) { }
$post = get_posts( 'p='.$id );
return apply_filters protected function update( $obj ) {}
( 'base_class_get_post', $post ); protected function delete( $obj ) {}
} }
} $sub = new subClass;
$my_post = array(
'post_title' => 'My post',
'post_content' => 'This is my post',
'post_status' => 'publish',
'post_author' => 1,
'post_category' => array( 8, 39 ) );
$sub->publish( $my_post );
PHP5 OOP + WordPress filters implementation

13. real-world example nextgen gallery

14. Problem: Solution:
We needed an additional function another_image_size( $image ) {
image size created to global $ngg;
if( !class_exists( 'ngg_Thumbnail' ) )
display in a lightbox within require_once( nggGallery::graphic_library() );
our theme. $image = nggdb::find_image( $image['id'] );
$width = '920';
$height = '560';
if ( !is_writable( $image->imagePath ) )
return ' <strong>'.$image->filename.
__( ' is not writeable','nggallery' ).'</strong>';
$file = new ngg_Thumbnail( $image->imagePath, TRUE );
if ( !$file->error ) {
$file->resize( $width, $height, 4 );
$image->imagePath = preg_replace(
'/(gif|jpg|jpeg|png)/i',
'lightbox.$1',
$image->imagePath );
$file->save( $image->imagePath,
$ngg->options['imgQuality']);
$size = @getimagesize ( $image->imagePath );
$file->destruct();
} else {
$file->destruct();
return ' <strong>'.$image->filename.
' (Error: '.$file->errmsg . ')</strong>';
}
}
add_action( 'ngg_added_new_image', 'another_image_size', 10, 1 );
real-world example: nextgen gallery

15. real-world example shopp plugin

16. Problem: Solution:
We wanted to use a real- function check_stock( $external, $product ) {
time external inventory if( !$stock = ExtInventory::checkStock( $product->ID ) )
return false;
tracking system.
return $stock;
}
add_filter( 'shopp_cartitem_stock', 'check_stock', 1, 2 );
real-world example: shopp plugin

17. real-world example social me

18. real-world example: social me
• custom post types for storing social media content
• opt-in extension manager
• extensions handle social networks

19. real-world example: social me twitter
• authenticates with oauth
• imports tweets as custom post type
• custom taxonomies for hash tags and @mentions
• post to twitter via actions
• changed defaults via filters

20. questions?

21. Brandon Dove
@brandondove
brandon@pixeljar.net
(714) 932-5787
http://pixeljar.net