pdo查询未运行

我似乎不明白为什么这个查询没有运行

if ( $productName && $productDescription && $productPrice ) {
// SQL
// UPDATE `prostud_tristurion`.`products` SET `product_title` = 'ajax test', `product_description` = 'Was certainty remaining engrossed applauded sir how discovery.', `product_price` = '524' WHERE `products`.`product_id` = 10;
try {
    $query = "update products set product_title = :pName, product_description = :pDescription, product_price = :pPrice, where product_id = :pid";
    //prepare query for excecution
    $stmt = $con->prepare($query);
    //bind the parameters
    $stmt->bindParam(':pid', $id);
    $stmt->bindParam(':pName', $productName);
    $stmt->bindParam(':pDescription', $productDescription);
    $stmt->bindParam(':pPrice', $productPrice);
    // echo "$productPrice / $productDescription / $productName / $id'n $stmt";
    var_dump($_POST);
    // Execute the query
    if ($stmt->execute() ) {
        echo "Record was updated.";
    } else {
        die('Unable to update record.');
    }
}catch(PDOException $exception){ //to handle error
    echo "Error: " . $exception->getMessage();
}
}

我得到的只是无法更新记录

var_dump($_POST); 

看起来不错