Code bật tắt khóa nội dung bài viết/trang

// Code thêm tuỳ chọn ẩn nội dung bài viết
class hiddencontentMetabox {
	private $screen = array(
		'post',
		'page',
	);
	private $meta_fields = array(
		array(
			'label' => 'Hide this content',
			'id' => 'bnix_hide_content',
			'default' => 'Ẩn nội dung bài này',
			'type' => 'checkbox',
		),
	);
	public function __construct() {
		add_action( 'add_meta_boxes', array( $this, 'add_meta_boxes' ) );
		add_action( 'save_post', array( $this, 'save_fields' ) );
	}
	public function add_meta_boxes() {
		foreach ( $this->screen as $single_screen ) {
			add_meta_box(
				'hiddencontent',
				__( 'Hidden Content', 'bnix' ),
				array( $this, 'meta_box_callback' ),
				$single_screen,
				'advanced',
				'default'
			);
		}
	}
	public function meta_box_callback( $post ) {
		wp_nonce_field( 'hiddencontent_data', 'hiddencontent_nonce' );
		echo 'Bật / tắt ẩn nội dung';
		$this->field_generator( $post );
	}
	public function field_generator( $post ) {
		$output = '';
		foreach ( $this->meta_fields as $meta_field ) {
			$label = '<label for="' . $meta_field['id'] . '">' . $meta_field['label'] . '</label>';
			$meta_value = get_post_meta( $post->ID, $meta_field['id'], true );
			if ( empty( $meta_value ) ) {
				$meta_value = $meta_field['default']; }
			switch ( $meta_field['type'] ) {
				case 'checkbox':
					$input = sprintf(
						'<input %s id=" % s" name="% s" type="checkbox" value="1">',
						$meta_value === '1' ? 'checked' : '',
						$meta_field['id'],
						$meta_field['id']
						);
					break;
				default:
					$input = sprintf(
						'<input %s id="%s" name="%s" type="%s" value="%s">',
						$meta_field['type'] !== 'color' ? 'style="width: 100%"' : '',
						$meta_field['id'],
						$meta_field['id'],
						$meta_field['type'],
						$meta_value
					);
			}
			$output .= $this->format_rows( $label, $input );
		}
		echo '<table class="form-table"><tbody>' . $output . '</tbody></table>';
	}
	public function format_rows( $label, $input ) {
		return '<tr><th>'.$label.'</th><td>'.$input.'</td></tr>';
	}
	public function save_fields( $post_id ) {
		if ( ! isset( $_POST['hiddencontent_nonce'] ) )
			return $post_id;
		$nonce = $_POST['hiddencontent_nonce'];
		if ( !wp_verify_nonce( $nonce, 'hiddencontent_data' ) )
			return $post_id;
		if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
			return $post_id;
		foreach ( $this->meta_fields as $meta_field ) {
			if ( isset( $_POST[ $meta_field['id'] ] ) ) {
				switch ( $meta_field['type'] ) {
					case 'email':
						$_POST[ $meta_field['id'] ] = sanitize_email( $_POST[ $meta_field['id'] ] );
						break;
					case 'text':
						$_POST[ $meta_field['id'] ] = sanitize_text_field( $_POST[ $meta_field['id'] ] );
						break;
				}
				update_post_meta( $post_id, $meta_field['id'], $_POST[ $meta_field['id'] ] );
			} else if ( $meta_field['type'] === 'checkbox' ) {
				update_post_meta( $post_id, $meta_field['id'], '0' );
			}
		}
	}
}
if (class_exists('hiddencontentMetabox')) {
	new hiddencontentMetabox;
};

add_filter( 'the_content', 'hide_content' );
function hide_content($content) {
	if(is_singular('post') || is_page()) {
		$hide = get_post_meta(get_the_ID(),'bnix_hide_content', true);
		if(is_user_logged_in() || !$hide) {
			return $content;
		}
		else {
			$box = '<div class="pc_warn_box">
						Bạn phải đăng nhập để được xem nội dung
						<div class="pc_warn_box_btn_wrap">						
							<a class="pc_warn_box_btn pc_login_trig" href="/wp-login.php?redirect_to='.urlencode(get_permalink()).'"><i class="fas fa-key"></i>Đăng Nhập</a>
							<a class="pc_warn_box_btn pc_registr_trig" href="/dang-ky"><i class="fas fa-thumbs-up"></i>Đăng Ký</a>
						</div>
					</div>';
			$box .= '<style>.pc_warn_box{border-color:#ffcc47;border-style:solid;border-width:4px 4px 4px 54px;border-radius:2px;line-height:normal;padding:11px 14px;position:relative;margin:20px auto;max-width:620px;margin-left:0 !important;}.pc_warn_box:before{content:"\f06a";font-family:"Font Awesome 5 Free",fontawesome;font-weight:900;position:absolute;left:-52px;top:50%;width:50px;text-align:center;height:30px;color:#fff;font-size:30px;line-height:26px;margin-top:-13px;text-shadow:2px 2px 6px rgba(100,100,100,.05);z-index:10}.pc_warn_box .pc_warn_box_btn{margin:12px 10px 1px 0!important;position:static!important;float:none!important;display:inline-block!important;text-decoration:none}.pc_warn_box_btn{background:#fefefe!important;border:1px solid #c5c5c5!important;border-radius:2px!important;box-shadow:none;color:#5f5f5f!important;padding:7px 15px!important;font-size:14px!important}.pc_warn_box i{font-size:98%;padding-right:8px}.pc_warn_box_btn:hover{background:#2d5386!important;border-color:#2d5386!important;color:#fff!important}</style>';
			return $box;
		}
	}
	else return $content;
}