Introduction to adding fixed fields to articles in wordpress

add_action( 'add_meta_boxes', 'myplugin_add_custom_box');
 

add_action( 'save_post', 'myplugin_save_postdata');function myplugin_add_custom_box() {
add_meta_box('myplugin_sectionid',
'设置缩略图', // 可自行修改标题文字
'myplugin_inner_custom_box',
'post');
}function myplugin_inner_custom_box( $post ) {
global $wpdb;
// Use nonce for verification
wp_nonce_field( plugin_basename( __FILE__ ), 
'myplugin_noncename' );
// 获取固定字段litpic的值，用于显示之前保存的值
// 此处wp_posts新添加的字段为litpic，多个用半角逗号隔开
$date = $wpdb->get_row( $wpdb->prepare( "SELECT litpic FROM $wpdb->posts WHERE ID = %d", $post->ID) );
// litpic  字段输入框的HTML代码
echo &#39;<label for="litpic_new_field">图片url </label>&#39;;
echo &#39;<input type="text" id="litpic_new_field" name="litpic_new_field" value="&#39;.$date->litpic.&#39;" size="28" />&#39;;
// 多个字段依此类推
}
function myplugin_save_postdata( $post_id ) {
// verify if this is an auto save routine.
// If it is our form has not been submitted, so we dont want to do anything
if ( defined( ’DOING_AUTOSAVE’ ) && DOING_AUTOSAVE )return;
// verify this came from the our screen and with proper authorization,
// because save_post can be triggered at other times
if ( !wp_verify_nonce( $_POST[&#39;myplugin_noncename&#39;], plugin_basename( __FILE__ ) ) )return;
// 权限验证
if ( &#39;post&#39; == $_POST[&#39;post_type&#39;] ) {
if ( !current_user_can( &#39;edit_post&#39;, $post_id ) )return;
}
// 获取编写文章时填写的固定字段的值，多个字段依此类推
$litpic = $_POST[&#39;litpic_new_field&#39;];global $wpdb;$wpdb->update( "$wpdb->posts",
// 以下一行代码，多个字段的话参照下面的写法，单引号中是字段名，右边是变量值。半角逗号隔开
array( &#39;litpic&#39; => $litpic),
array( &#39;ID&#39; => $post_id ),
// 添加了多少个新字段就写多少个%s，半角逗号隔开
array( &#39;%s&#39;),
array( &#39;%d&#39;)
);
}

if ( ! empty( $schema['properties']['litpic'] ) ) {            
$data['litpic'] = $post->litpic;
        }

'litpic'        => array(                    
'description' => __( 'A litpic to protect access to the content and excerpt.' ),
                    'type'        => 'string',
                    'context'     => array( 'view', 'edit', 'embed' ),
                ),

$post_type_attributes = array(            'title',
            'editor',
            'author',
            'excerpt',
            'thumbnail',
            'comments',
            'revisions',
            'page-attributes',
            'post-formats',
            'custom-fields',
            'litpic',
        );        $fixed_schemas = array(            'post' => array(                'title',
                'editor',
                'author',
                'excerpt',
                'thumbnail',
                'comments',
                'revisions',
                'post-formats',
                'custom-fields',
                'litpic',
            ),

case 'litpic':                    
$schema['properties']['litpic'] = array(                        
'description' => __( 'The ID for the litpic of the object.' ),
                        'type'        => 'string',
                        'context'     => array( 'view', 'edit', 'embed' ),
                    );                    break;