update_post_meta() 不断向数组中添加，而不是替换值。有什么建议吗？

以前我用过add_post_meta() 这是偶然的，也许它以某种方式将场标记为一个数组？

更新，那么如何将元字段设置为非数组？

代码：

$lowjobtrig = 1;    
foreach ( $values as $value ) :


    //====================myedit==================

    if ($key == \'public_paywall\') {
        if ($value == \'paywall\') {
            add_post_meta($postId, $key, $value, /*unique=*/ false);
        } elseif ($value == \'public\'{
            add_post_meta($postId, $key, $value, /*unique=*/ false);                        
        } 

    } elseif ($key == \'pay_offer\') {
        if ($value == \'pay\') {
            add_post_meta($postId, $key, $value, false);
        } elseif ($value == \'no pay\') {
            add_post_meta($postId, $key, $value, false);    
        } else {
        }

    } elseif ($key == \'low_jobs\' AND $value == \'under 100\'){
        $lowjobtrig = 1;
        update_post_meta($postId, $key, \'under 100\');   

    } elseif ($key == \'low_jobs\' AND $value != \'under 100\' AND $lowjobtrig == 0){
        add_post_meta($postId, $key, \'OVER 100\', true); 
        $lowjobtrig = 1;             
    }

    else {
        FeedWordPress::diagnostic(\'syndicated_posts:meta_data\', ">>>>>>>>>>ELSE Adding post meta-datum to post [$postId]: [$key] = ".MyPHP::val($value, /*no newlines=*/ true));                            
        add_post_meta($postId, $key, $value, /*unique=*/ false);

    }