Error on enabling login module

				<div id="fb-root"></div>

				<script src="//connect.facebook.net/en_US/all.js"></script>

				<script>

					var jfbconnectRequestPerms = null;
 
					FB.init({appId: '107461229296562', status: true, cookie: true, xfbml: true});

                                        function fb_login_button_click()

                                        {
                                            // A user has logged in, and a new cookie has been saved

                                            var session = FB.getSession();
                                            var ajaxUrl = "https://dev.cloud-canvas.com/index.php?option=com_jfbconnect&tmpl=component&task=getRequestPerms&fb_user_id=" + session.uid;
                                            var ajax = new Ajax(ajaxUrl, { evalScripts: true});//, onComplete: fb_login_button_click2 });
                                            ajax.request();
                                        }

                                        function fb_logout_button_click()

                                        {
                                                redirect_to_jfbconnect_logout()
                                        }

                                        function redirect_to_jfbconnect_logout()
                                        {
                                            window.location = '/index.php/component/jfbconnect/?task=logout&return=aW5kZXgucGhw';
                                        }

				</script>
<br />
<b>Fatal error</b>:  Uncaught exception 'Exception' with message 'Facebook needs the JSON PHP extension.' in /var/www/html/administrator/components/com_jfbconnect/assets/facebook-api/facebook.php:15
Stack trace:
#0 /var/www/html/components/com_jfbconnect/libraries/facebook.php(111): include_once()
#1 /var/www/html/components/com_jfbconnect/libraries/facebook.php(35): JFBConnectFacebookLibrary->getFbClient()
#2 /var/www/html/components/com_jfbconnect/libraries/facebook.php(23): JFBConnectFacebookLibrary->__construct()
#3 /var/www/html/modules/mod_jfbclogin/mod_jfbclogin.php(15): JFBConnectFacebookLibrary::getInstance()
#4 /var/www/html/libraries/joomla/application/module/helper.php(173): require('/var/www/html/m...')
#5 /var/www/html/libraries/joomla/document/html/renderer/module.php(84): JModuleHelper->renderModule(Object(stdClass), Array)
#6 /var/www/html/libraries/joomla/document/html/renderer/modules.php(41): JDocumentRendererModule->render(Object(stdClass), Array, NULL)
#7 /var/www/html/libraries/joomla/document/html/html.php in <b>/var/www/html/administrator/components/com_jfbconnect/assets/facebook-api/facebook.php</b> on line <b>15</b><br />