mysqli_stmt_close() expects parameter 1 to be mysqli_stmt, boolean given in C:\wamp64\www\web\form11.php on line 101

Question

I load the form, and I don't get any mysqli_stmt_close() error on the form file. When I submit data from the form to database, I get mysqli_stmt_close() error. See below the code from the INSERT STATEMENT.

$sql = "INSERT INTO manpower, payments (grade_level, number_of_staff, year, consolidated_salary, perculiar_allowance, conpss_salaries) VALUES (?, ?, ?, ?, ?, ?)";

    if($stmt = mysqli_prepare($link, $sql)){
         var_dump($stmt);

        // Bind variables to the prepared statement as parameters
        mysqli_stmt_bind_param($stmt, 'ssssss' ,$param_grade_level, $param_number_of_staff, $param_year, $param_consolidated_salary,
        $param_perculiar_allowance, $param_conpss_salaries);


        // Attempt to execute the prepared statement
        if(mysqli_stmt_execute($stmt)){
            // Records created successfully. Redirect to landing page
            header("location: grid1.php");
            exit();
        } else{
            echo "Something went wrong. Please try again later.";
        }
    }

     // Close statement
    mysqli_stmt_close($stmt);
}