Php qualification system mysql

Well here with a doubt:

I currently have a user rating system.

My question is how could I save the id of the user I want to qualify for, so that after doing a SELECT I bring in console all the comments and the rating that user has.

The code is like this:

<?php
session_start();
require'conexion.php';

if(!isset($_SESSION["id_usuario"])){
   header("Location: index.php");
}
?>

<?php
$sql = "SELECT id FROM usuarios WHERE id = ?";   
$id = $_GET['id'];
$stmt = $mysqli->prepare($sql);

if ($stmt) {

$stmt->bind_param("i", $id);
$stmt->execute();
$stmt->store_result();

$statement = mi_fetchassoc($stmt);

       }


function mi_fetchassoc($stmt)
{
if($stmt->num_rows>0)
{
    $rs = array();
    $md = $stmt->result_metadata();
    $params = array();
    while($field = $md->fetch_field()) {
        $params[] = &$rs[$field->name];
    }
    call_user_func_array(array($stmt, 'bind_result'), $params);
    if($stmt->fetch())
        return $rs;
}

return null;
}

?>

<?php 
require "conexion.php";
if(isset($_POST)){
if(mysqli_query($mysqli,"INSERT INTO comentarios (comentario, rating, usuario, fecha, id_us) VALUES ('".$_POST['comentario']."', '".$_POST['rating']."', '".$_SESSION['id_usuario']."', NOW(), '".$statement['id']."')")){
    echo "1";       
}else{
    echo "2";
}
}
?>

Where:

Comment: it's the buyer's opinion.

Rating: is the value from 1 to 5 in qualification.

User: Here I save the user id of the current session. BUYER

Date: the now brings the current date.

id_us: Here I want to save the id of the user I am qualifying to and where the error is marked. SELLER

TABLE of comments:

id primary key int (11) auto increment not null,

comment varchar (100) not null,

rating int (11) not null,

user varchar (30) not null,

datetime default null date,

id_us int (11)

TABLE users:

id int (11) primary key not null auto_increment,

user varchar (30) not null,

email varchar (30) not null,

pw varchar (30) not null,

name varchar (30) not null.

I hope someone can solve this doubt.

Thank you.