WordPress Transients API: Cache Database Queries for Better Performance (wppioneer.com)

01-snippet.php

set_transient( 'my_cache_key', $data, HOUR_IN_SECONDS );
$cached = get_transient( 'my_cache_key' );
delete_transient( 'my_cache_key' );

02-snippet.txt

set_site_transient( 'my_network_cache', $data, DAY_IN_SECONDS );
get_site_transient( 'my_network_cache' );
delete_site_transient( 'my_network_cache' );

03-my-get-popular-posts.php

function my_get_popular_posts() {
 $cache_key = 'popular_posts_v1';
 $popular = get_transient( $cache_key );

 if ( false === $popular ) {
 $popular = get_posts( [
 'post_type' => 'post',
 'posts_per_page' => 10,
 'meta_key' => 'post_views',
 'orderby' => 'meta_value_num',
 'order' => 'DESC',
 ] );
 set_transient( $cache_key, $popular, HOUR_IN_SECONDS );
 }

 return $popular;
}

04-my-get-weather.php

function my_get_weather( $city ) {
 $cache_key = 'weather_' . md5( $city );
 $weather = get_transient( $cache_key );

 if ( false === $weather ) {
 $response = wp_remote_get( "https://api.weather.example/?q=$city" );
 if ( ! is_wp_error( $response ) && 200 === wp_remote_retrieve_response_code( $response ) ) {
 $weather = json_decode( wp_remote_retrieve_body( $response ), true );
 set_transient( $cache_key, $weather, 15 * MINUTE_IN_SECONDS );
 } else {
 // Cache the failure briefly so we do not hammer a broken API.
 set_transient( $cache_key, [ 'error' => true ], MINUTE_IN_SECONDS );
 return [];
 }
 }

 return isset( $weather['error'] ) ? [] : $weather;
}

05-snippet.php

wp_cache_set( 'my_key', $data, 'my_group', 300 );
$data = wp_cache_get( 'my_key', 'my_group', false, $found );

06-wp.sh

wp transient list
wp transient get popular_posts_v1
wp transient delete popular_posts_v1
wp transient delete --all # nuclear option; useful after schema changes