Wordpress Metabox Wrapper

custom_metabox.php

<?php

class custom_metabox {

	//Custom metabox key
	public $key = 'meta_box_key';

	//Custom metabox options
	public $options = array(
			'post_types'  => get_post_types(),
			'title'       => 'Meta Box Title',
			'context'     => 'side', //normal, advanced, side
			'priority'    => 'low', //default, core, high, low
			'description' => ''
		);

	public function custom_meta_add(){

		foreach( $this->options->post_types as $post_type ){
			//$key, $title, $callback, $post_type, $context, $priority, $callback_args
			add_meta_box(
				$this->key,
				esc_html__( $this->options->title ),
				array(&$this, 'custom_meta_render' ),
				$post_type,
				$this->options->context,
				$this->options->priority,
				$callback_args = null
			);
		}

	}

	public function custom_meta_render( $object, $box ){

		wp_nonce_field( basename( __FILE__ ), $this->key.'_nonce' );

		$data = get_post_meta( $object->ID, $this->key, true );

		//Render metabox HTML
		//<input type="text" class="widefat" value="" />

	}

	public function custom_meta_save( $post_id, $post = false ){

		//Verify nonce
		if ( !isset( $_POST[$this->key.'_nonce'] ) || !wp_verify_nonce( $_POST[$this->key.'_nonce'], basename( __FILE__ ) ) ){
			return $post_id;
		}

		//Check posted data
		$new_meta_value = ( isset( $_POST[$this->key] ) ? $_POST[$this->key] : '' );

		//Get previously saved data
		$meta_value = get_post_meta( $post_id, $this->key, true );

		//Add, update and delete data
		if( $new_meta_value && '' == $meta_value ){
			add_post_meta( $post_id, $this->key, $new_meta_value, true );
		} elseif ( $new_meta_value && $new_meta_value != $meta_value ){
			update_post_meta( $post_id, $key, $new_meta_value );
		} elseif ( '' == $new_meta_value && $meta_value ){
			delete_post_meta( $post_id, $key, $meta_value );
		}

	}

	public function custom_meta_setup() {

		//Add metaox
		add_action( 'add_meta_boxes', array( &$this, 'custom_meta_add' ) );
		//Save metabox
		add_action( 'save_post', array( &$this, 'custom_meta_save' ) );

	}

	public function __construct( $params = array() ){

		//Create options object
		$this->options = (object)$this->options;
		//Add custom metabox
		add_action( 'init', array( &$this, 'custom_meta_setup' ) );

	}

}

new custom_metabox();