original.php

<?php
/**
 * deargodwhy Metabox
 *
 * @package deargodwhy
 */

add_action( 'add_meta_boxes', 'deargodwhy_add_sidebar_layout_box', 10, 2 );

function deargodwhy_add_sidebar_layout_box( $type, $post ) {
	add_meta_box(
		'deargodwhy_sidebar_layout',
		__( 'Sidebar Layout', 'deargodwhy' ),
		'deargodwhy_sidebar_layout_callback',
		'page',
		'normal',
		'high'
	);
}

function deargodwhy_sidebar_layout_callback( $post ) {
	$layouts = array(
		'right-sidebar' => array(
			'value'     => 'right-sidebar',
			'label'     => __( 'Right Sidebar(default)', 'deargodwhy' ),
			'thumbnail' => get_template_directory_uri() . '/images/right-sidebar.png',
		),
		'no-sidebar' => array(
			'value'     => 'no-sidebar',
			'label'     => __( 'No Sidebar','deargodwhy' ),
			'thumbnail' => get_template_directory_uri() . '/images/no-sidebar.png',
		),
	);

	wp_nonce_field( basename( __FILE__ ), 'deargodwhy_nonce' );
?>

<table class="form-table">
	<tr>
		<td colspan="4"><em class="f13"><?php esc_html_e( 'Choose Sidebar Template', 'deargodwhy' ); ?></em></td>
	</tr>

	<tr>
		<td>
		<?php
		// Create a default value for the setting.
		$layout = get_post_meta( $post->ID, 'deargodwhy_sidebar_layout', true );
		if ( empty( $layout ) ) {
			$meta = 'right-sidebar';
		}

		foreach ( $layouts as $field ) {
			?>
			<div class="radio-image-wrapper">
				<label class="description">
					<span><img src="<?php echo esc_url( $field['thumbnail'] ); ?>"/></span><br/>
<input type="radio" name="deargodwhy_sidebar_layout" value="<?php echo esc_attr( $field['value'] ); ?>" <?php checked( $field['value'], $layout ); ?>/>&nbsp;<?php echo esc_html( $field['label'] ); ?>
				</label>
			</div>
			<?php } // End foreach().
			?>
			<div class="clear"></div>
		</td>
	</tr>
</table>
<?php
}

/**
 * save the custom metabox data
 * @hooked to save_post hook
 */
function deargodwhy_save_sidebar_layout( $post_id ) {

	// Verify the nonce before proceeding.
	if ( ! isset( $_POST['deargodwhy_nonce'] ) || ! wp_verify_nonce( $_POST['deargodwhy_nonce'], basename( __FILE__ ) ) ) {
		return;
	}

	// Stop WP from clearing custom fields on autosave
	if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
		return;
	}

	if ( 'page' === $_POST['post_type'] ) {
		if ( ! current_user_can( 'edit_page', $post_id ) ) {
			return $post_id;
		}
	} elseif ( ! current_user_can( 'edit_post', $post_id ) ) {
			return $post_id;
	}

	if ( ! empty( $_POST['deargodwhy_sidebar_layout'] )
		&& in_array( $_POST['deargodwhy_sidebar_layout'], array( 'right-sidebar', 'no-sidebar' ), true )
		) {
		update_post_meta( $post_id, 'deargodwhy_sidebar_layout', $_POST['deargodwhy_sidebar_layout'] );
	}
}
add_action( 'save_post' , 'deargodwhy_save_sidebar_layout' );