Prepared query isn't working PHP - php

Question

I'm trying to use prepared queries, but this code isn't working, it just stucks on the first use of prepare(). Commenting the fist if() does nothing, now it stucks on the second. No connection problems/no errors, just stuck.
If I do all of this using just mysqli_query() everything works great.
function addUser($id){
/*
if ($stmt = $this->mysqli->prepare("SELECT * FROM Users WHERE ID = ?")){
if (!($stmt->bind_param("s", $id))){
return false;
}
if ($stmt->execute()) {
if ($stmt->num_rows!=0){
return false;
}
}else{
return false;
}
}else{
return false;
}*/
if ($stmt = $this->mysqli->prepare("INSERT INTO Users VALUES (?, '')")) {
if (!$stmt->bind_param("s", $id)) {
return false;
}
if (!$stmt->execute()) {
return false;
}
return true;
}
return false;
}
and about debugging, if i change the code like this
function addUser($id){
echo "1";
if ($stmt = $this->mysqli->prepare("SELECT * FROM Users WHERE ID = ?")){
echo "2";
if (!($stmt->bind_param("s", $id))){
return false;
} ...
}else{
echo "3";
} ...
I'll see only "1" on the page.
start of the class:
class db{
private $mysqli;
function __construct($ip, $login, $password, $database){
$this->mysqli = new mysqli($ip, $login, $password, $database) or die("Problem with DB connection!");
$this->mysqli->set_charset("utf8");
}

Answer 1

You never execute() so nothing will happen, therefore no errors will raise.
Here is how I would write it:
function addUser($id){
if ($this->mysqli->connect_errno) {
die('Connect Error: ' . $this->mysqli->connect_errno);
}
if ($stmt = $this->mysqli->prepare("INSERT INTO Users VALUES (?, '')")) {
$stmt->bind_param("s", $id);//did you mean i for type int ?
$stmt->execute();//dont forget this!!
}else{
die('Connect Error: ' . $this->mysqli->connect_errno);
}
return ($stmt->rowCount() > 0)? true : false;
}