下面是获取项目列表、返回第一个项目并显示第一个id中的单个图像的四个示例。

• explode 假设数据位于由逗号分隔的字符串中。

• get_attached_media 提取帖子中的所有附加项目，然后呈现该列表中的第一个项目

• get_post_meta 假设数据存在于一个数组中——为了进行测试，它将创建一个ID数组

• get_post_custom_values 似乎将post meta拉入未序列化状态，因此您需要运行maybe_unserialize;

// get your custom field data (this looks like your meta_value)

$meta_value = "378,377,376,375,374,373"; 

// convert csv to array

$ids = explode ( \',\', $meta_value );

// pull the first item out as the variable $id

list($id) = $ids;

// show the image

echo wp_get_attachment_image ( $id, \'medium\' );

// assume you have these vals
$post = get_post();
$post_id = $post->ID;

// get the attachments
$attachments = get_attached_media(\'image\', $post_id);
if(count($attachments) > 0) {
    $first_attachment = array_shift($attachments);
    echo wp_get_attachment_image($first_attachment->ID);
}

$post = get_post();
$post_id = $post->ID;
$key = \'attachment\';

$generate_if_not_found = false; // for testing
if($generate_if_not_found && empty(get_post_meta($post_id, $key, true))) {
    // write the values if we don\'t have them
    update_post_meta($post_id, $key, array(386, 393, 234, 23, 23, 234));
}

$ids = get_post_meta($post_id, $key, true);
if( ! empty($ids) && count($ids) > 0) {
    $first_id = array_shift($ids);
    echo wp_get_attachment_image($first_id);
}

$post = get_post();
$post_id = $post->ID;
$key = \'attachment\';

if(is_array($value = get_post_custom_values($key, $post_id))) {
    if(count($value) > 0) {
        if(is_array($ids = maybe_unserialize($value[ 0 ]))) {
            if(count($ids) > 0) {
                $id = array_shift($ids);
                echo wp_get_attachment_image($id);
            }
        }
    }
}

Custom Column

function posts_render_custom_columns($column_name, $post_id) {
    if($column_name === \'attachment\') {

        $size = \'thumbnail\';

        $attachments = get_attached_media(\'image\', $post_id);
        if(count($attachments) > 0) {
            $first_attachment = array_shift($attachments);
            echo wp_get_attachment_image($first_attachment->ID, $size);
        }
    }
}