How to fix “mysqli_stmt::bind_param():” on modification to mysql databas

Question

I am creating a user registration system, and I am at the point where I start modifying the database i get the error "Warning: mysqli_stmt::bind_param(): Number of elements in type definition string doesn't match number of bind variables in /opt/lampp/htdocs/Projectss/01_sarah/index.php on line 41 "

I have tried using every single method in php documentation concerning adding data to the database

here is some code

       $hash_password = password_hash($password, PASSWORD_DEFAULT);

        $query = "INSERT INTO users (first_name,last_name,email,password) VALUES('$first_name','$last_name','$email','$hash_password')";

        $stmt = $conn->prepare($query);
        if (!$stmt) {
            echo mysqli_error($conn);
        }
        $stmt->bind_param('ssss', $query);
        $stmt->execute(); // execute prepared statement
        $conn->close(); // close connection

    }

The expected result should is to not receive any warning after saving the information to the database

Answer 1

You're passing complete query in the bindParam and also passing the values in the query instead of this you need to pass the parameters in the bindParam like this..

       $hash_password = password_hash($password, PASSWORD_DEFAULT);

    $query = "INSERT INTO users (first_name,last_name,email,password) VALUES(?, ?, ?, ?)";

    $stmt = $conn->prepare($query);
    $stmt->bind_param('ssss', $first_name, $last_name, $email, $hash_password);
    $stmt->execute(); // execute prepared statement
    $conn->close(); // close connection