2. What I'm going to cover
The WordPress page lifecycle.
What are hooks and how do they fit into the page lifecycle?
Why use hooks?
What are actions
What are filters
Examples
3. The WP page lifecycle
"A page life cycle is nothing more than a combination of the
events that take place from when a browser requests a
page to when the server returns the page to the browser."
Lets look at loading a single page in WP
- Look at the requested page ID
- Query the database
- Get associated data (Categories, tags, images, etc)
- Return all of the data to the browser
4. The WP page lifecycle
The template files and the calls to the API
functions are then responsible for rendering,
styling and position the data on the screen
Sounds simple but this is just a simple page
load. Think of more complex sites WP sites you
have been on.
You can now understand how intensive this
particular process can be.
5.
6. The WP page lifecycle
"While WordPress is running its series of queries and
preparing to render data back to the browser, it’s looking at
all of the custom hooks – that is, the actions and filters –
that have been written and is passing data through those
filters before returning data to the browser."
At this point it's important to define what hooks
are and look at the difference between action
and filter hooks and how they play into this
whole lifecycle
7. What are hooks and why use them?
They are the backbone of WordPress.
They enable developers to "hook" into the WP
lifecycle to change how it works without
modifying the core code.
Developers hook code is separate from WP
core so that WP updates don't remove or
destroy the developers code.
11. Examples
Changing the excerpt length on the home page:
function wpldn_excerpt( $length ) {
if ( is_home() ) {
return 20;
}
return $length;
}
add_filter( 'excerpt_length', 'wpldn_excerpt', 999 );
12. Examples
Adding Google Maps JS to contact us page
function wpldn_maps_js() {
if ( !is_page( 'contact-us' ) ) {
return;
}
wp_enqueue_scripts( 'google_maps_api',
'[PATH_TO_GOOGLE_MAP_API]', array(), false, true
);
wp_enqueue_scripts( 'my_map_js', '[PATH_TO_YOUR_JS]',
array( 'google_maps_api' ), false, true );
}
add_action( 'wp_enqueue_scripts', 'wpldn_maps_js' );
13. Examples
Load a different theme template file at will
function wpldn_any_file() {
if( !is_page( "about-us" ) ) {
return;
}
include( '/path/to/any/file.extension' );
exit();
}
add_action( 'template_redirect', 'wpldn_any_file' );
14. Examples
Using pre_get_posts to change the main query
function wpldn_change_query( $query ) {
if( $query->is_home() && $query->is_main_query() ) {
$query->set( 'posts_per_page', 20 );
}
}
add_action( 'pre_get_posts', 'wpldn_change_query' );
15. Examples
Remove that pesky capital_P_dangit function
remove_filter( 'the_title', 'capital_P_dangit', 11 );
remove_filter( 'the_content', 'capital_P_dangit', 11 );
remove_filter( 'comment_text', 'capital_P_dangit', 31 );
* Check /wp-includes/default-filters.php to see what functions WP
is applying to its own filters
18. Don't be scared!
Rummage around in core code to find filters
and hooks that are not documented.
A good knowledge of PHP will help you to find
and understand WordPress hooks.
IDEs can help in navigating through WP core
code.
