$mysqli = new mysqli('ip', 'user', 'pass',  'dbname');

$post = filter_input_array(INPUT_POST);
 if (isset($post)) {



     $skills = $mysqli->real_escape_string($post['skills']);

     if (isset($post['email'])) {
         $temp_email= $post['email'];

         $sql = $mysqli->query("SELECT email FROM users WHERE email='$temp_email'");
        if ($sql->num_rows > 0) {
          $msg = "email already exists!";
       } else {
             $email = $temp_email;
       }
     } else {
         $msg = "Please enter your email!";
     }

     if (isset($post['username'])) {
         $temp_username= $post['username'];

         $sql = $mysqli->query("SELECT username FROM users WHERE username='$temp_username'");
        if ($sql->num_rows > 0) {
          $msg = "Username already exists!";
       } else {
             $username = $temp_username;
       }
     } else {
         $msg = "Please enter your username!";
     }


     if (isset($post['password'])) {
         if ($post['password'] === $post['confirmpassword']) {

             $password = password_hash($password, PASSWORD_BCRYPT); //hash and bcrypt adds a level of security for the password so once it's saved into the database it will be saved as something else
         } else {
             $msg = "Two passwords do not match!";
         }
     } else {
         $msg = "Please enter your password!";
     }


     if(isset($post['captcha'])) {
         if ($post['captcha'] === $_SESSION['captcha']) {
     } else {
            $msg = "The captcha is not correct";
      }
     } else {
         $msg = "Please enter the captcha";
     }

     if(isset($email) && isset($username) && isset($password)) {
        //if the query is successful, redirect to emailvalidation.php page
             $mysqli->query("INSERT INTO users (username,email,password,skills,active,activationCode)
                      VALUES ('$username', '$email', '$password','$skills', '0', '$activationCodeString');
                      ");
            // $mysqli->query($sql);
     }