meta-box.php

<?php
/**
 * Plugin Name: Meta Box
 * Plugin URI:  https://metabox.io
 * Description: Create custom meta boxes and custom fields in WordPress.
 * Version:     5.0.1
 * Author:      MetaBox.io
 * Author URI:  https://metabox.io
 * License:     GPL2+
 * Text Domain: meta-box
 * Domain Path: /languages/
 *
 * @package Meta Box
 */

if ( defined( 'ABSPATH' ) && ! defined( 'RWMB_VER' ) ) {
	register_activation_hook( __FILE__, 'rwmb_check_php_version' );

	/**
	 * Display notice for old PHP version.
	 */
	function rwmb_check_php_version() {
		if ( version_compare( phpversion(), '5.3', '<' ) ) {
			die( esc_html__( 'Meta Box requires PHP version 5.3+. Please contact your host to upgrade.', 'meta-box' ) );
		}
	}

	require_once dirname( __FILE__ ) . '/inc/loader.php';
	$rwmb_loader = new RWMB_Loader();
	$rwmb_loader->init();
}