Php script error

 
public function storeUser($name, $email, $password) {
        $uuid = uniqid('', true);
        $hash = $this->hashSSHA($password);
        $encrypted_password = $hash["encrypted"]; // encrypted password
        $salt = $hash["salt"]; // salt
 
        $stmt = $this->conn->prepare("INSERT INTO users(unique_id, name, email, encrypted_password, salt, created_at) VALUES(?, ?, ?, ?, ?, NOW())");
        $stmt->bind_param("sssss", $uuid, $name, $email, $encrypted_password, $salt);
        $result = $stmt->execute();
        $stmt->close();
 
        // check for successful store
        if ($result) {
            $stmt = $this->conn->prepare("SELECT * FROM users WHERE email = ?");
            $stmt->bind_param("s", $email);
            $stmt->execute();
            $user = $stmt->get_result()->fetch_assoc();
            $stmt->close();
 
            return $user;
        } else {
            return false;
        }
    }
    /**
     * Get user by email and password
     */
    public function getUserByEmailAndPassword($email, $password) {
 
        $stmt = $this->conn->prepare("SELECT * FROM users WHERE email = ?");
 
        $stmt->bind_param("s", $email);
 
        if ($stmt->execute()) {
            $user = $stmt->get_result()->fetch_assoc();
            $stmt->close();
 
            // verifying user password
            $salt = $user['salt'];
            $encrypted_password = $user['encrypted_password'];
            $hash = $this->checkhashSSHA($salt, $password);
            // check for password equality
            if ($encrypted_password == $hash) {
                // user authentication details are correct
                return $user;
            }
        } else {
            return NULL;
        }
    }

 "D/RegisterActivity: Login Response:  <br />
                    <b>Fatal error</b>:  Call to a member function bind_param() on a non-object in <b>...\include\DB_Functions.php</b> on line <b>50</b><br /> 

 $stmt->bind_param("s", $email);