A quick and easy guide to WordPress Transients

1. Transients:
Temporary Cache Assistance

2. “... offers a simple and standardized way of
storing cached data in the database temporarily
by giving it a custom name and a timeframe after
which it will expire and be deleted.”

3. set_transient(
$transient,
$value,
$expiration
);

4. $transient
• (string) a unique identifier for your cached data
• 45 characters or less

5. $value
• (array|object) Data to save, either a regular variable or
an array/object
• Handles serialization of complex data for you

6. $expiration
• (integer) number of seconds to keep the data before
refreshing
• Example: 60*60*24 or 86400 (24 hours)

7. MINUTE_IN_SECONDS = 60
HOUR_IN_SECONDS = 60 * MINUTE_IN_SECONDS
DAY_IN_SECONDS = 24 * HOUR_IN_SECONDS
WEEK_IN_SECONDS = 7 * DAY_IN_SECONDS
YEAR_IN_SECONDS = 365 * DAY_IN_SECONDS

8. get_transient($transient);
• Returns false if the transient doesn’t exist or has
expired
• An integar value of zero/empty could be the stored
data, so always check for false
• Should not be used to hold plain boolean values; use
array, string, or integer instead

9. delete_transient($transient);

10. Once a transient expires, it remains in the
database until it is refreshed or deleted.

11. Basic Example:
Store a query

12. function ut_get_ticker_items() {
$args = array(
'post_type' => array( 'news-items', 'event' ),
'posts_per_page' => 99,
'taxonomy' => 'news_categories',
'term' => 'ticker',
);
$posts = new WP_Query( $args );
return $posts;
}

13. function ut_get_ticker_items() {
if ( false === ( $posts = get_transient( 'ticker_items' ) ) ) {
$args = array(
'post_type' => array( 'news-items', 'event' ),
'posts_per_page' => 99,
'taxonomy' => 'news_categories',
'term' => 'ticker',
);
$posts = new WP_Query( $args );
set_transient( 'ticker_items', $posts, WEEK_IN_SECONDS );
}
return $posts;
}

14. function ut_refresh_ticker_items( $post_id, $post_obj ) {
$post_type = $post_obj->post_type;
if ( in_array( $post_type, array( 'news-items', 'event' ) ) ) {
delete_transient( 'ticker_items' );
}
}
add_action( 'save_post', 'ut_refresh_ticker_items', 10, 2 );
add_action( 'deleted_post', 'ut_refresh_ticker_items', 10, 2 );

15. Advanced Example:
Store user’s search results

16. function ws_set_search_string() {
global $wp_query;
$wp_session = WP_Session::get_instance();
if ( is_admin() === false && is_search() === true && isset( $wp_query->query_vars_hash )
=== true ) {
$search_string = $wp_query->query['s'];
$search_hash = $wp_query->query_vars_hash;
$wp_session['search_string'] = $search_string;
$wp_session['search_hash'] = $search_hash;
$wp_session['search_array'] = ws_search_array( $search_hash );
}
if ( is_admin() === false && is_search() === false && is_attachment() === false && is_
main_query() === true ) {
$wp_session['search_string'] = null;
$wp_session['search_hash'] = null;
$wp_session['search_array'] = null;
}
}
add_action( 'pre_get_posts', 'ws_set_search_string' );

17. function ws_search_array( $search_hash ) {
if ( false === ( $search_array = get_transient( 'ws_search_' . $search_hash ) ) ) {
global $wpdb;
$posts = $wpdb->get_results( $GLOBALS['wp_query']->request );
if ( empty( $posts ) === false ) {
$search_array = array();
foreach ( $posts as $post ) {
$search_array[] = $post->ID;
}
}
// save the transient for 10 minutes
set_transient( 'ws_search_' . $search_hash, $search_array, HOURS_IN_SECONDS * 6 );
}
return $search_array;
}

18. function ws_get_next_search_result( $next = true ) {
$wp_session = WP_Session::get_instance();
if ( isset( $wp_session['search_array'] ) === false ) {
return false;
}
$next_location = 0;
$search_array = $wp_session['search_array']->toArray();
$location = array_search( get_the_ID(), $search_array );
if ( $next === true ) {
$next_location = $location + 1;
if ( isset( $search_array[$next_location] ) === false ) {
$next_location = 0;
}
} else {
$next_location = $location - 1;
if ( isset( $search_array[$next_location] ) === false ) {
end( $search_array );
$next_location = key( $search_array );
}
}
return $search_array[$next_location];
}

19. function ws_post_nav() {
$prev = $next = null;
if ( ws_get_next_search_result() ) {
$prev = get_post( ws_get_next_search_result( false ) );
$next = get_post( ws_get_next_search_result() );
} else {
$prev = get_previous_post( true );
$next = get_next_post( true );
}
// output previous and next post links with get_permalink( $next->ID )
}

20. The End