users registar php

<?php

# 1. importar a ligação
require_once("connection.php");

if(isset($_GET['registar'])){
$table="users";
$username=addslashes($_GET['username']);
$sql="SELECT id FROM $table WHERE username LIKE '$username'";
$query=mysqli_query($connect,$sql);
$total=mysqli_num_rows($query);

if($total==0){
    #posso registar
$sql="INSERT INTO $table (username) VALUES
('$username')";
mysqli_query($connect,$sql) or die($sql);

$idUser=mysqli_insert_id($connect);
$table="passwords";
$password=addslashes($_GET['psw']);
$sql="INSERT INTO $table(idUser,psw) VALUES
($idUser,'$password')";
mysqli_query($connect,$sql) or die($sql);

$table="users_privilegios";
$idPrivilegio=4;
$idOperador=3;
$sql="INSERT INTO $table (idUser,idPrivilegio,idOperador)
VALUES ($idUser,$idPrivilegio,$idOperador)";
mysqli_query($connect,$sql) or die($sql);   
$caminho="?sucesso";
} else{
    #username repetido 
$caminho="?fracasso";   
}
header("Location:$caminho");
}
?>