Fatal error after tried to fix update statement - php

Question

I tried to make the update statement to be safety againts sql injection but its give me this erro Fatal error: Call to a member function bind_param() on a non-object on line 39
$pid = $_POST['pid'];
$pagetitle = $_POST['pagetitle'];
$linklabel = $_POST['linklabel'];
$keyword = $_POST['keyword'];
$descriere = $_POST['descriere'];
$data = $_POST['data'];
$pagebody = $_POST['pagebody'];
// Filter Function -------------------------------------------------------------------
function filterFunction ($var) {
$var = nl2br(htmlspecialchars($var));
$var = str_replace("/", "\\\\", $var);
$var = preg_replace("~/~", "\\\\", $var);
return $var;
}
$pagetitle = filterFunction($pagetitle);
$linklabel = filterFunction($linklabel);
$keyword = filterFunction($keyword);
$descriere = filterFunction($descriere);
$data = filterFunction($data);
$pagebody = filterFunction($pagebody);
// End Filter Function --------------------------------------------------------------
include_once "../conx.php";
// Add the updated info into the database table
$stmt = $con->prepare("UPDATE pages SET (pagetitle, linklabel, keywords, description, pagebody, lastmodified) VALUES (?, ?, ?, ?, ?, ?) WHERE id = ?");
// TODO check that $stmt creation succeeded
// "s" means the database expects a string
$stmt->bind_param("sssssss", $pagetitle, $linklabel, $keyword, $descriere, $pagebody, $data, $pid);
$stmt->execute();
$stmt->close();
line 39 is $stmt->bind_param("sssssss", $pagetitle, $linklabel, $keyword, $descriere, $pagebody, $data, $pid);
it is necessary to make this or i can revert to how it was before
$query = mysqli_query($con, "UPDATE pages SET pagetitle='$pagetitle', linklabel='$linklabel', pagebody='$pagebody', lastmodified='now()' WHERE id='$pid'") or die (mysqli_error($con));

Answer 1

Didn't this produce an error?
$con->prepare("UPDATE pages SET (pagetitle, linklabel, keywords, description, pagebody, lastmodified) VALUES (?, ?, ?, ?, ?, ?) WHERE id = ?");
this should be
$con->prepare("UPDATE pages SET pagetitle=?, linklabel=?, keywords=?, description=?, pagebody=?, lastmodified=? WHERE id = ?");
Refer: http://dev.mysql.com/doc/refman/5.7/en/update.html
now you can proceed to bind parameters
$stmt->bind_param("sssssss", $pagetitle, $linklabel, $keyword, $descriere, $pagebody, $data, $pid);