email notification box

<?php

/* what show on custom box */
function print_my_custom_notification_box( $post ) {
    wp_nonce_field( 'my_custom_notification_box_nonce_action', 'my_custom_notification_box_nonce_field' ); ?>
    <script type="text/javascript">
    jQuery(document).ready(function(){
        $('#mynotification-box-button').click(function(e){
            e.preventDefault();
            $('#mynotification-box .spinner').show();
            $.ajax({ url: ajaxurl, data: { action: 'sendnotification', postID: $('#post_ID').val(), my_notification_nonce: $('#my_custom_notification_box_nonce_field').val() },
                success: function(content){
                    $('#mynotification').text(content).css('visibility','visible');
                    setTimeout(function(){
                        $('#mynotification').empty().css({'visibility':'hidden'});
                    },3000)
                    $('#mynotification-box .spinner').hide();
                }
            });
        });
    });
    </script>
    <div class="submitbox" id="mynotification-box" style="padding: 10px 0 0;clear: both;border-top: 1px solid whiteSmoke;margin-top: -2px;">
        <input type="submit" class="button button-primary button-large" id="mynotification-box-button" accesskey="n" value="Send Email Notification" style="float:right">
        <span class="spinner" style="display: none;"></span>
        <div class="clear"></div>
        <p id="mynotification" style="visibility: hidden; height: 1em; margin: 5px 0 10px; text-align: right;"></p>
    </div>
<?php
}
// add our custom box
function my_custom_notification_box() {
    $posttype = array( 'post', 'page' );
    foreach ($posttype as $type) {
        add_meta_box(
            'post_email_notification',
            __( 'Email Notification'),
            'print_my_custom_notification_box',
            $type,
            'side',
            'core'
        );
    }
}
add_action( 'add_meta_boxes', 'my_custom_notification_box' );

/* send email function */
function send_mypost_notification(){
    if(!wp_verify_nonce( $_GET['my_notification_nonce'],  'my_custom_notification_box_nonce_action' ))
        die;

    $postID = $_GET['postID'];

    $firstname = get_post_meta($postID, 'first_name', true);
    $surname = get_post_meta($postID, 'surname', true);
    $email = get_post_meta($postID, 'surname', true);

    $subject = get_bloginfo('name').' Notification';
    $headers = 'From: '.get_bloginfo('name').' <'.get_bloginfo('admin_email').'>' . "\r\n";
    $message = 'Hello '.$firstname.',\n\n Your page has been updated.\n <a href="'.get_permalink($postID).'" target="_blank">Click here to view your page.</a>\n\n From the team.\n <a href="'.get_bloginfo('url').'" target="_blank">'.get_bloginfo('url').'</a>';

    $send_success = wp_mail( $email, $subject, $message, $headers, $attachments );

    if($send_success)
        echo 'Notification is successfully sent';
    else
        echo 'Notification failed to sent';
    die;
}
add_action('wp_ajax_sendnotification', 'send_mypost_notification');


?>