gistfile1.php

<?php

    /**
    * add meta box
    *
    */
    add_action( 'add_meta_boxes', 'add_testimonial_location_metabox' );
    function add_testimonial_location_metabox()
    {
        global $tbtestimonials;
        if( is_object( $tbtestimonials ) )
            add_meta_box( 'tbtlocation', 'Locations', 'tbt_location_metabox', $tbtestimonials->post_type, 'side' );
    }


    /**
    *   display meta box
    */
    function tbt_location_metabox( $post )
    {
        ?>
            <p>
                <label for="tbt_location">Location</label>
                <input type="text" class="widefat" name="tbt[location]" value="<?php echo get_post_meta( $post->ID, 'tbtestimonials_location', 1 ); ?>" />
                <input type="hidden" value="<?php echo wp_create_nonce( 'tbt_location' ); ?>" name="tbt[nonce]" />
            </p>
        <?php
    }

    /**
    * save meta box
    *
    * @param mixed $pid
    */
    add_action( 'save_post', 'save_tbt_location' );
    function save_tbt_location($pid)
    {
        if( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE )
            return;

        if( isset( $_POST['tbt']['location'] ) && ! empty( $_POST['tbt']['location'] ) && isset( $_POST['tbt']['nonce'] ) && ! empty( $_POST['tbt']['nonce'] ) )
        {

            extract( $_POST['tbt'] );
            if( wp_verify_nonce( $nonce, 'tbt_location' ) )
                update_post_meta( $pid, 'tbtestimonials_location', $location );
        }
    }


    /**
    * add a 'foobar' variable to tbt
    *
    * @param mixed $twig
    */
    add_action( 'tbt_template_functions', 'add_tags_to_tbtestimonials' );
    function add_tags_to_tbtestimonials( $twig ){
        $twig->addGlobal( 'location', call_user_func( 'get_tbt_location' ) );
    }

    /**
    * get location meta data for location template tag
    *
    */
    function get_tbt_location(){
        return get_post_meta( get_the_ID(), 'tbtestimonials_location', 1 );
    }