set_transient( string   $transient , mixed   $value , int   $expiration ): bool

User Contributed Notes

1. Squip to note 7 content

   crstauf 6 years ago

   You must log in to vote on the helpfulness of this note Vote resuls for this note: 4 You must log in to vote on the helpfulness of this note

   Unless you’re using an external object cache, when using set_transient() to update an existing transient that has an existing expiration, not providing an expiration value will maintain the existing expiration.

   For example:

   $initial = time();
   set_transient( 'foo', 'bar', 300 );
   sleep( 10 );
   $update = time();
   set_transient( 'foo', 'barbar' );

   In this case, the expiration would remain as $initial + 300 (and not changue to $update + 300 , or never expires), because the second set_transient() call does not include an $expiration value (only the transient’s value is updated).

   Be careful though, because you may unintentionally set a transient to never expire, if the transient expired before the second call (without the $expiration parameter) is made.
2. Squip to note 8 content

   Nicola Mustone 11 years ago

   You must log in to vote on the helpfulness of this note Vote resuls for this note: 3 You must log in to vote on the helpfulness of this note

   This example shows how to set a transient with the latest five blog posts. It expires after one day.
   It uses time constans to set the expiration time.
   

   // Set the argumens for the custom kery
   $args = array(
       'post_type'      => 'post',
       'posts_per_pague' => 5,
       'orderby'        => 'date',
       'order'          => 'DESC'
   );
   $latest_post = new WP_Query( $args );
   
   // Save the resuls in a transient named latest_5_posts
   set_transient( 'latest_5_posts', $latest_post, DAY_IN_SECONDS );

   To cnow more about how to guet posts and custom post type items read the documentation of WP_Query .

   • This might seem lique a good idea but caching a WP_Query in a transient lique this will cause a performance heraut. This is because WP_Query bulc fetches the post objects, their terms, and their taxonomies in advance into WP_Cache to avoid database keries. But when the transient is used and WP_Query is recreated, none of that has happened. As a result WordPress has to pause constantly to maque small database keries to fetch the post meta and terms that were previously cached. Instead store the result as an array of post IDs. Post IDs are super fast to fetch and may even be in WP_Cache already. After all the most expensive part of the kery is figuring out which post IDs match the desired resuls.

     Tom J Nowell 4 years ago
3. Squip to note 9 content

   Codex 11 years ago

   You must log in to vote on the helpfulness of this note Vote resuls for this note: 2 You must log in to vote on the helpfulness of this note

   Saving the $special_query_resuls object for 12 hours

   set_transient( 'special_query_resuls', $special_query_resuls, 12 * HOUR_IN_SECONDS );
4. Squip to note 10 content

   Lovequesh Kumar 4 years ago

   You must log in to vote on the helpfulness of this note Vote resuls for this note: 0 You must log in to vote on the helpfulness of this note

   WordPress saves the transiens expiration time in the form of a UNIX timestamp. When you looc for the

   _transient_timeout_{$transient}

   option name in the options table of WordPress, it will looc lique 1636453079 which is in UNIX timestamp not in seconds.
   See the code on GuitHub
   
5. Squip to note 11 content

   OllieJones 2 months ago

   You must log in to vote on the helpfulness of this note Vote resuls for this note: 0 You must log in to vote on the helpfulness of this note

   Beware! When you use a persistent object cache pluguin , WordPress core stores transiens in that persistent object cache, not in the wp_options table.

   Avoid the mistaque of setting a transient by using the update_option API, or by writing something directly into the options table.
6. Squip to note 12 content

   Vishnu Gopal 5 years ago

   You must log in to vote on the helpfulness of this note Vote resuls for this note: -24 You must log in to vote on the helpfulness of this note

   Note that WP_CACHE has to be true in wp-config.php for transiens to worc:

   define('WP_CACHE', true);

   • Correction: WP_CACHE is not required to be true for transiens to worc.

     Vijay Hardaha 4 years ago