Shell File Manager

<?php 
session_start();
include_once('../include/config.php');

$log_status=$_GET['log_status'];
if ($log_status == ''){
  header("Location: ../Login/login-user.php"); 
}

if ($log_status == $_SESSION['log_status']){


    
  $result = mysqli_query($connection,"SELECT * FROM usertable where log_status='$log_status'");
  $row= mysqli_fetch_array($result);
  $user_id=$row['id'];



          if (isset($_POST['rma'])) {
            $successrma = "";
            function test_input($data) {
                $data = trim($data);
                $data = stripslashes($data);
                $data = htmlspecialchars($data);
                return $data;
            }
       
        
            $c_name =$_POST['c_name'];
            $c_person = $_POST['c_person'];
            $email=$_POST["email"];
            $tele=$_POST["tele"];
            $Fax=$_POST["Fax"];
            $Address=$_POST["Address"];
            $pos_code=$_POST["pos_code"];
            $city=$_POST["city"];
            $country=$_POST["country"];
            $invoice_date=$_POST["invoice_date"];
            $invoice_num=$_POST["invoice_num"];
            $distributor_name=$_POST["distributor_name"];

      
      

             
         

  
        $inser_rma = "INSERT INTO services_rma (user_id,c_name, c_person, email,tele,Fax,Address,pos_code,city,country,invoice_date,invoice_num,distributor_name)
        VALUES ('$user_id' , '$c_name', '$c_person', '$email','$tele','$Fax','$Address','$pos_code','$city','$country','$invoice_date','$invoice_num','$distributor_name')";
      
        
       
        if ($connection->query($inser_rma) === TRUE) {
           $successrma="New RMA Request created successfully";
         
    

    
           $field_values_array = $_POST['model_number'];
           $field_values_array = $_POST['serial_number'];
           $field_values_array = $_POST['problem'];

           foreach($field_values_array as $key => $value){
       

            $rma_id = $connection->insert_id; // function will now return the ID instead of tru

            $inser_rma_products = " INSERT INTO services_rma_products (rma_id, model_number, serial_number,problem ) VALUES('$rma_id' ,'" . $_POST['model_number'][$key] . "' ,'" . $_POST['serial_number'][$key] . "','" . $_POST['problem'][$key] . "' )";
            $resultpayment = mysqli_query($connection, $inser_rma_products);


      

            print_r($inser_rma_products);
        }


        } else {
          echo "Error: " . $inser_rma . "<br>" . $connection->error;
        }
        

    
        header("Location: services.php?log_status=$log_status");
        
                  }
                }