<?php config.php ?>
<?php $stmt = $conn->prepare("SELECT * FROM user where user_id = :user_id");
$stmt->bindValue('user_id', $_GET['id']);
$stmt->execute();
while($user = $stmt->fetch(PDO::FETCH_OBJ)){
echo "form stuff to echo the fields value" ;
} ?>

if (isset($_POST['save'])) {
error_reporting(E_ERROR | E_PARSE | E_CORE_ERROR);
$sql = $conn->prepare("UPDATE user SET username = :username, password = :password, firstname = :firstname, lastname =:lastname where user_id = :user_id");
$sql->bindParam(":user_id",$_POST["user_id"],PDO::PARAM_INT);
$sql->bindParam(":username",$_POST["username"],PDO::PARAM_STR);
$sql->bindParam(":password",$_POST["password"],PDO::PARAM_STR);
$sql->bindParam(":firstname",$_POST["firstname"],PDO::PARAM_STR);
$sql->bindParam(":lastname",$_POST["lastname"],PDO::PARAM_STR);
if($sql->execute()){
echo "Successfully updated ";
}
else {
echo "Not updated";
}
} ?>