demo for tomas

class TP_Primo_Featured_Image_Options_Custom_Meta_Box {

	public function __construct() {

		if ( is_admin() ) {
			add_action( 'load-post.php',     array( $this, 'init_metabox' ) );
			add_action( 'load-post-new.php', array( $this, 'init_metabox' ) );
		}

	}

	public function init_metabox() {

		add_action( 'add_meta_boxes',        array( $this, 'add_metabox' )         );
		add_action( 'save_post',             array( $this, 'save_metabox' ), 10, 2 );

	}

	public function add_metabox() {

		add_meta_box(
			'featured-image-options',
			__( 'Featured Image Options', 'tp-primo' ),
			array( $this, 'render_tp_primo_featured_image_options_metabox' ),
			array( 'post', 'page' ),
			'side',
			'default'
		);

	}

	public function render_tp_primo_featured_image_options_metabox( $post ) {

		// Add nonce for security and authentication.
		wp_nonce_field( 'tp_primo_nonce_action', 'tp_primo_nonce' );

		// Retrieve an existing value from the database.
		$tp_primo_where_to_show = get_post_meta( $post->ID, 'tp_primo_where_to_show', true );

		// Set default values.
		if( empty( $tp_primo_where_to_show ) ) $tp_primo_where_to_show = '';

		// Form fields.
		echo '<table class="form-table">';

		echo '	<tr>';
		echo '		<th><label for="tp_primo_where_to_show" class="tp_primo_where_to_show_label">' . __( 'Where to Show', 'tp-primo' ) . '</label></th>';
		echo '		<td>';
		echo '			<label><input type="radio" name="tp_primo_where_to_show" class="tp_primo_where_to_show_field" value="tp_primo_above" ' . checked( $tp_primo_where_to_show, 'tp_primo_above', false ) . '> ' . __( 'Show Above Title', 'tp-primo' ) . '</label><br>';
		echo '			<label><input type="radio" name="tp_primo_where_to_show" class="tp_primo_where_to_show_field" value="tp_primo_bellow" ' . checked( $tp_primo_where_to_show, 'tp_primo_bellow', false ) . '> ' . __( 'Show Below Title', 'tp-primo' ) . '</label><br>';
		echo '		</td>';
		echo '	</tr>';

		echo '</table>';

	}

	public function save_metabox( $post_id, $post ) {

		// Add nonce for security and authentication.
		$nonce_name   = isset( $_POST['tp_primo_nonce'] ) ? $_POST['tp_primo_nonce'] : '';
		$nonce_action = 'tp_primo_nonce_action';

		// Check if a nonce is set.
		if ( ! isset( $nonce_name ) )
			return;

		// Check if a nonce is valid.
		if ( ! wp_verify_nonce( $nonce_name, $nonce_action ) )
			return;

		// Check if the user has permissions to save data.
		if ( ! current_user_can( 'edit_post', $post_id ) )
			return;

		// Check if it's not an autosave.
		if ( wp_is_post_autosave( $post_id ) )
			return;

		// Check if it's not a revision.
		if ( wp_is_post_revision( $post_id ) )
			return;

		// Sanitize user input.
		$tp_primo_new_where_to_show = isset( $_POST[ 'tp_primo_where_to_show' ] ) ? $_POST[ 'tp_primo_where_to_show' ] : '';

		// Update the meta field in the database.
		update_post_meta( $post_id, 'tp_primo_where_to_show', $tp_primo_new_where_to_show );

	}

}

new TP_Primo_Featured_Image_Options_Custom_Meta_Box;