wp_cache_get( int|string $key, string $group = '', bool $force = false, bool $found = null ): mixed|false

User Contributed Notes

1. Skip to note 5 content

   sun 2 years ago

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   Here is how you use the $found parameter in your code – it is passed by reference, so you do not need to define the variable upfront, its value will be set by the called function instead:

   $value = wp_cache_get( 'wpdocs_mykey', 'wpdocs_mygroup', false, $found );
   
   if ( ! $found) {
       $value = wpdocs_my_expensive_function();
       wp_cache_set( 'wpdocs_mykey', $value, 'wpdocs_mygroup' );
   }
   
   return $value;

   You need to use the $found parameter if there is a slightest chance that the value you are caching can be zero, false, null, or otherwise equivalent to false (falsy) like an empty array.

   If you are not sure, or if you are looking for a general rule of thumb – always use the $found parameter.

   If some object caches are not implementing the $found parameter correctly, then that is a good reason to fix those implementations (or use better maintained ones) and not a reason to not use the parameter.
2. Skip to note 6 content

   Mayeenul Islam 7 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 1You must log in to vote on the helpfulness of this note

   function prefix_get_post_count( $post_status = 'publish' ) {
       $cache_key = 'prefix_post_count_'. $post_status;
       $_posts = wp_cache_get( $cache_key );
       if ( false === $_posts ) {
           $_posts = $wpdb->get_var(
                       $wpdb->prepare(
                           "SELECT COUNT(*) FROM $wpdb->posts WHERE post_type = 'post' AND post_status = %s",
                           $post_status
                       ));
    
           wp_cache_set( $cache_key, $_posts );
       }
    
       return $_posts;
   }
3. Skip to note 7 content

   Aamer Shahzad 5 years ago

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   /**
    * Handles the users column output.
    *
    * @since 4.3.0
    *
    * @param array $blog Current site.
    */
   public function column_users( $blog ) {
       $user_count = wp_cache_get( $blog['blog_id'] . '_user_count', 'blog-details' );
       if ( ! $user_count ) {
           $blog_users = new WP_User_Query(
               array(
                   'blog_id'     => $blog['blog_id'],
                   'fields'      => 'ID',
                   'number'      => 1,
                   'count_total' => true,
               )
           );
           $user_count = $blog_users->get_total();
           wp_cache_set( $blog['blog_id'] . '_user_count', $user_count, 'blog-details', 12 * HOUR_IN_SECONDS );
       }
   
       printf(
           '<a href="%s">%s</a>',
           esc_url( network_admin_url( 'site-users.php?id=' . $blog['blog_id'] ) ),
           number_format_i18n( $user_count )
       );
   }

   • Unless I misunderstand, I believe the result of get_total() will always be zero or one, because the query is limited to one user per page of results with the number parameter.

     crstauf 5 years ago
4. Skip to note 8 content

   Michael Nelson 3 years ago

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   It seems some cache dropins (like those used on WPEngine) may define `wp_cache_get` WITHOUT the 4th parameter, `$found`. This means `$found` might not be populated by `wp_cache_get() ` (it will always be `null`, regardless of whether the value was cached or not), and you can also get a ton of warnings as reported here and here.

   The workaround? Pretend `$found` isn’t an argument, and never use `wp_cache_set() ` to cache a value of `false` (because you won’t be able to differentiate a cached value of `false` from the lack of a cached value, where `wp_cache_get() ` also returns `false`.)

   Eg
   [PHP]
   $result = wp_get_cache(‘my_key’);
   if( $result === false){
   // calculate the result, and use `0` or `null` instead of `false`
   if( $result === false){
   $result = 0;
   }
   wp_cache_set(‘my_key’, $result);
   }
   [/php]