Database wont update

This is doing my head in. 

I have another page on a different table (same database) where this works fine. Yet now when I try to update the record, the eventbody (text area) just echos the data with formatting and it says "unable to update record" - which is defined error.

All I did was change the field names on this page...

Hope you can help 

<?php
error_reporting(E_ALL);
  ini_set("display_errors", 1);

//include database connection

include 'db_connect.php';

//check any user action

$action = isset( $_POST['action'] ) ? $_POST['action'] : "";

if($action == "update"){ //if the user hit the submit button

//write our update query

//$mysqli->real_escape_string() function helps us prevent attacks such as SQL injection

$query = "update eventguide 

set

eventtitle = '".$mysqli->real_escape_string($_POST['eventtitle'])."',
eventbody = '".$mysqli->real_escape_string($_POST['eventbody'])."',
eventdate = '".$mysqli->real_escape_string($_POST['eventdate'])."',
where eventid = S'".$mysqli->real_escape_string($_REQUEST['eventid'])."'";

//execute the query

if( $mysqli->query($query) ) {

//if updating the record was successful

echo "<h1><strong>User was updated.</strong></h1>";

}else{

//if unable to update new record

echo "Database Error: Unable to update record.";

}

}

//select the specific database record to update

$query = "select eventid, eventtitle, eventbody, eventdate

from eventguide

where eventid = '".$mysqli->real_escape_string($_REQUEST['eventid'])."'

limit 0,1";

//execute the query

$result = $mysqli->query( $query );

//get the result

$row = $result->fetch_assoc();

//assign the result to certain variable so our html form will be filled up with values

$eventid = $row['eventid'];

$eventtitle = $row['eventtitle'];

$eventbody = $row['eventbody'];

$eventdate = $row['eventdate'];


?>