PDO SQL Statement Not Working - php

Question

I've been looking at this for the last hour and cannot see why this wont work? It is carried out in a bootstrap modal via AJAX.
For some reason SupplierUpdate will not get updated in the database. (It is a timestamp)
$conn = new PDO("mysql:host=$hostname; dbname=$username;charset=utf8", $username, $password, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES 'utf8'"));
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "UPDATE Suppliers SET UpdateTime=:UpdateTime, Code1=:Code1, Code1Desc=:Code1Desc, Code2=:Code2, Code2Desc=:Code2Desc, Code3=:Code3, Code3Desc=:Code3Desc WHERE UserID ='$UserID'";
$stmt = $conn->prepare($sql);
$stmt->bindParam(':Code1', $_POST['Code1'], PDO::PARAM_STR);
$stmt->bindParam(':Code1Desc', $_POST['Code1Desc'], PDO::PARAM_STR);
$stmt->bindParam(':Code2', $_POST['Code2'], PDO::PARAM_STR);
$stmt->bindParam(':Code2Desc', $_POST['Code2Desc'], PDO::PARAM_STR);
$stmt->bindParam(':Code3', $_POST['Code3'], PDO::PARAM_STR);
$stmt->bindParam(':Code3Desc', $_POST['Code3Desc'], PDO::PARAM_STR);
$stmt->bindParam(':UpdateTime', $_POST['Update'], PDO::PARAM_STR);
$stmt->execute();
<input type="text" name="SupplierUpdate" id="SupplierUpdate" value="<?php echo $timestamp ?>">

Answer 1

Your input type name="SupplierUpdate"
But i dont see you are binding it with this name
you are using $_POST['Update']

Answer 2

you may try to debug it like below...
if($conn){
$stmt = $conn->prepare($sql);
}
else{
echo "not connected";
}
Then, set your date format forcefully like,
$upd_tim = date('Y-m-d H:i:s', strtotime($_POST['Update']));
$stmt->bindParam(':UpdateTime', $upd_tim, PDO::PARAM_STR);
Then, after the execute(),
echo $stmt->rowCount();