How to add Meta box to wordpress admin post page

This article will tell you about, How to add Meta box to wordpress admin post and page.Use following code and create wordpressapi.php file and upload this file to wp-content/plugins/ folder.

<?php
/*
Plugin Name:  WordPressapi Meta Box
Plugin URI: http://images.purabtech.in/
Description: Adding the Meta box to admin panel -> post
Version: 0.0
Author: WordPressapi
Author URI: http://images.purabtech.in/
*/

function wordpressapi_meta_box() {
add_meta_box(
'wordpressapi',
'Wordpressapi Box', //Meta box title
'write_in_meta_box',
'post' // You can define here where to add the Meta box(post, page, link)
);
}

function write_in_meta_box(){
echo "Wordpressapi is writing something in admin meta box";
}

if (is_admin())
add_action('admin_menu', 'wordpressapi_meta_box');
?>

Go to your Plugin tab and activate the “WordPressapi Meta Box” plugin.
After activating the plugin you are able to see the Meta box on post page.