Parse error: syntax error, unexpected '(', expecting variable (T_VARIABLE) in C:\xampp\htdocs\Expert\class\users.php on line 10

Question

<?php

    class users{
    public $host="localhost";
    public $username="root";
    public $pass="";
    public $db_name="testing";
    public $conn;

    public function_construct()
    {
        $this-> conn=new mysqli($this->host,$this->username,$this->pass,$this->db_name);

        if($this-> conn->connect_errno)
        {
            die("database connection failed".$this-> conn->connect_errno);
        }
    }

    public function signup($data)
    {
        $this-> conn->query($data);
    }
}
?>