Add Policy Number to policy metadata

[jschumann]

    /* Adds a meta box to the post edit screen */
    add_action( 'add_meta_boxes', 'policy_add_custom_box' );
    function policy_add_custom_box( $post ) {
        $screens = array( 'post', 'my_cpt' );
        foreach ( $screens as $screen ) {
            add_meta_box(
                'policy_box_number',            // Unique ID
                'Number',                                                   // Box title
                'policy_inner_custom_box',          // Content callback
                 $screen                                    // post type
            );
        }
    }

    /* Prints the box content */
    function policy_number_custom_box( $post ) {
    ?>
       <label for="policy_number"> Number </label>
        <input name="policy_number" id="policy_number" class="postbox" />
    <?php
    }

    add_action( 'save_post', 'policy_save_postdata' );
    function policy_save_postdata( $post_id ) {
        if ( array_key_exists('myplugin_field', $_POST ) ) {
            update_post_meta( $post_id,
               '_my_meta_value_key',
                $_POST['myplugin_field']
            );
        }
    }