Question

我使用以下代码查找最新评论的ID。我将值缓存3秒。

function get_most_recent_comment_id() {
global $wpdb;

$transName = 'mostRecentCommentID'; // Name of value in trans.
$cacheTime = 3; // Time in seconds between updates.

// Check if value is in the cache
if (false === ($response = get_transient($transName) ) )
{

    $max_comment_id = $wpdb->get_var( "SELECT MAX( comment_id ) FROM wp_comments;");
    $response = $max_comment_id;
    set_transient($transName, $response, $cacheTime);
}

wp_send_json( $response );

}

然而它一直在回归Null。我做错了什么？

Answer 1

此行存在一些潜在问题：

$max_comment_id = $wpdb->get_var( "SELECT MAX( comment_id ) FROM FROM wp_comments;");

＆＃34; FROM＆＃34;给出两次，并且可能不需要wp_comments之后的分号。尝试：

$max_comment_id = $wpdb->get_var( "SELECT MAX( comment_id ) FROM wp_comments");

Answer 2

尝试将$ db对象作为参数传递给函数

function get_most_recent_comment_id($db) {
$transName = 'mostRecentCommentID'; // Name of value in trans.
$cacheTime = 3; // Time in seconds between updates.
// Check if value is in the cache
if (false === ($response = get_transient($transName) ) )
{
$max_comment_id = $db->get_var( "SELECT MAX( comment_id ) FROM wp_comments;");
$response = $max_comment_id;
set_transient($transName, $response, $cacheTime);
}
wp_send_json( $response );
}

用$ wpdb对象调用你的函数

function get_most_recent_comment_id($wpdb);

get_var不返回值

2 个答案: