Sample using jQuery

function register_settings()
{

    register_setting('Pixel_Redirect_Single_17','Pixel_Redirect_Single','Pixel_Redirect_plugin_maintenance');
}


function Pixel_Redirect_plugin_maintenance($options)
{

    if(isset($options) AND $options['license_key']!='')
    {
        $settings['license_key'] = $options['license_key'];

        $license = $options['license_key'];

        $api_params = array('action' => 'activate_license','license' => $license,'item_name' => urlencode('fb-pixel-redirect'),'domain' => $_SERVER['SERVER_NAME']);

        $response = wp_remote_get(add_query_arg($api_params,'http://www.licenseengine.com/licenses/a/'),array('timeout' => 15,'sslverify' => false));
        if(is_wp_error($response))
        {
            return false;
        }
        $license_data = json_decode(wp_remote_retrieve_body($response));

        if(!empty($license_data) AND $license_data->license=='valid')
        {
            $data = array('timestamp' => time());

            update_option('Pixel_Redirect_Single_17-lks',serialize($data));

            return $settings;
        }
        elseif(!empty($license_data) AND $license_data->license=='invalid')
        {
            update_option('Pixel_Redirect_Single_17-lks',$license_data->license);

            return $settings;
        }
        else
        {
            return false;
        }

    }
}

function get_all_options()
{

    $l = get_option('Pixel_Redirect_Single_17');

    $v = get_option('Pixel_Redirect_Single_17-lks');

    $u = FALSE;
    if(isset($v))
    {
        $data = unserialize($v);
        if($data['timestamp']>time()-24*60*60)
        {
            return true;
        }
    }
    if($u===FALSE)
    {
        $api_params = array('action' => 'activate_license','license' => $l['license_key'],'item_name' => 'wpsmartlinks','domain' => urlencode($_SERVER['SERVER_NAME']));

        $response = wp_remote_get(add_query_arg($api_params,'http://www.licenseengine.com/licenses/a/'),array('timeout' => 15,'sslverify' => false));

        if(is_wp_error($response))
        {
            return false;
        }

        $license_data = json_decode(wp_remote_retrieve_body($response));

        if(!empty($license_data) AND $license_data->license=='valid')
        {
            $data = array('timestamp' => time());

            update_option('wpsmartlinks_11-lks',serialize($data));

            return true;
        }
        elseif(!empty($license_data) AND $license_data->license=='invalid')
        {
            update_option('wpsmartlinks_11-lks',$license_data->license);

            return false;
        }
        else
        {
            return false;
        }
    }
}


function in_admin_footer()
{

    $PTYPE = get_post_type();
    if($PTYPE=='redirect')
    {

        $status = get_all_options();

        if($status==false)
        {

            echo <<<END
<div id='license' style='display:none'>
    <div style="padding: 15px; font-size: 14px;">
        <div class="alert alert-error" style="margin-top:10px;color:red;">
            Your License Key is NOT Valid.
        </div>
        <h4><?php _e('Registration'); ?></h4>

        <form method="post" action="options.php" enctype="multipart/form-data" id="license_key">

            <?php settings_fields('wp_action_image_27'); ?>

            <div class="button-container">
                <input id="license_key" name="wp_action_image_27[license_key]" type="text" class="input-xlarge" placeholder="Enter Your License Key" value=""/>
                <input type="submit" value="Save" id="save_button" class="button action"/>

                <p>Can't find your key? Login to
                    <a href="//www.licenseengine.com/my-keys" target="_blank">License Engine</a> to retrieve your key.
                </p>
            </div>
        </form>
        <div style="margin-top:10px;margin-left:185px;">
            <img src="//www.licenseengine.com/assets2/img/licensingpoweredbyLE.png"></div>
    </div>
</div>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script type="application/javascript">
    jQuery(document).ready(function () {
        html = jQuery('#license').html();
        jQuery('.wrap').first().before(html).css('display', 'none');
    });

</script>
END;

        }

    }
}

add_action('admin_init','register_settings');