Caching in WordPress provides three main ways to cache content: 1. Page caching stores entire page outputs to serve static content and avoid database queries on repeat visits. 2. Transients cache query and object results, like recent posts, and are stored in the database for retrieval until expiration. 3. Object caching stores content in memory for faster loading, but requires an external persistent data store like Memcached to remain available between page loads.

1. Caching in WordPress
Tareq Hasan (@tareq_cse)
http://tareq.weDevs.com

2. What is Caching?
• Serve static content to the visitor without querying
the database.
• Not generated upon **every** request
• Reduce to API calls

3. Type of Caching?
• Page Cache - Whole page as static content
• Query Cache - Cache SQL query results
• Fragment Cache - Cache a piece of page
• Browser Cache - Cache page assets
• Opcode Cache - PHP executes faster

4. WordPress Caching APIs
Transients!
- Persistent out of the box
- Stored in wp_options
get_transient()
set_transient()
delete_transient()
Object Cache!
- Not persistent without a
persistent backend
- Storage depends on the
backend
wp_cache_add()
wp_cache_set()
wp_cache_get()
wp_cache_delete()

5. Using Transients
set_transient( $key, $value, $expiration );
<?php
// Get any existing copy of our transient data
$special_query = get_transient( 'special_query' );
if ( false === $special_query_results ) {
$special_query = new WP_Query( 'cat=5&order=random' );
set_transient( 'special_query', $special_query, 12 * HOUR_IN_SECONDS );
}
// Use the data like you would have normally...
Queries only after each 12 hours

6. Object Cache
• Not persistent. Means, valid for only one pageload
• Requires a persistent backend. Such as APC,
Memcached.
• Plugins like W3 Total Cache, Memcached Object
Cache helps.
• Used Extensively in WordPress
• Cache objects can be grouped

7. Object Cache Functions
// set the cache with value
wp_cache_add( $key, $data, $group, $expire )
wp_cache_set( $key, $data, $group, $expire )
// retrieve the value from cache
wp_cache_get( $key, $group )
// clears data from the cache for the given key.
wp_cache_replace( $key, $data, $group, $expire )
// clears all cached data.
wp_cache_flush()

8. Using Object Cache
$result = wp_cache_get( 'my_result' );
if ( false === $result ) {
$result = $wpdb->get_results( $query );
wp_cache_set( 'my_result', $result );
}
// Do something with $result;
http://codex.wordpress.org/Class_Reference/WP_Object_Cache

9. Persistent Cache Plugins
• W3 Total Cache
• WP File Cache
• Memcached Object Cache
• APC Object Cache
• WordPress Redis Backend

10. Fragment Caching
• Cache a fragment of a page
• This could be your menubar, widgets and other
query related parts.
https://gist.github.com/markjaquith/2653957

11. Browser Caching
• HTTP Cache-Control
• Expiry Headers
• Entity Tags
(W3-Total-Cache, WP Super Cache)
http://www.mobify.com/blog/beginners-guide-to-http-cache-headers/

12. Opcode Cache
php-apc + W3 Total Cache

13. Questions?