I'm testing a new site on XAMPP. I have run into this notice:
Notice: A non well formed numeric value encountered in D:\xampp\htdocs\marksman\includes\register.inc.php on line 17
Code below

class RegisterUser extends Db{
     private $fullname;
     private $emailaddress;
     private $username;
     private $password;
     private $passwordRepeat;
     private $emailCode;

     public function registerUsers(){
         if(isset($_POST['register-submit'])){
           $this->fullname = $_POST['fullname'];
           $this->emailaddress = $_POST['emailaddress'];
           $this->username = $_POST['username'];
           $this->password = $_POST['password'];
           $this->passwordRepeat = $_POST['passwordRepeat'];
           $this->emailCode = PASSWORD_HASH($this->username,PASSWORD_DEFAULT + microtime());//the notice is from here

The issue is solved now. I needed to cast the microtime(); as an integer.
Like:

PASSWORD_HASH($this->username,PASSWORD_DEFAULT + (int)microtime());