Protect access to files on my system (php)

Use the following measures to protect my system without having to change the database.

  

SESSIONS:

<?php   
       if ((isset($_SESSION['conectado']) && ($_SESSION['conectado'] == true) && ($_SESSION['nivel']==0) && ($_SESSION['nivel']==1)))
       {
    } else {
   echo ('<script>alert("No tiene permisos suficientes para acceder a esta parte del sistema");</script>');
   echo ("<script>window.location = 'index.php';</script>");
   exit;
   }
   $now = time();
   if($now > $_SESSION['expira']) {
   session_destroy();
   echo ('<script>alert("Su sesi\u00f3n ha expirado");</script>');
   echo ("<script>window.location = 'index.php';</script>");
   exit;
   }
   ?>

  

MENUS

<?php
   session_start();
   include_once 'sesion_todos.php';
?>

  

ACTIONS

 <?php
    $temp = $_POST["temp"];

    if ($temp == 1)
      {

      }
      else
      {
      echo ('<script>alert("No tiene permisos suficientes para acceder a esta parte del sistema");</script>');
      echo ("<script>window.location = 'index.php';</script>");
      }

    ?>

Here I give you the example, I hope it serves you. Basically what you have to do is create two tables, one for the menu and the second for the permissions. The permit table if you have to relate it to the user's.

Structure of the menu table:

CREATE TABLE IF NOT EXISTS menu (
  id int(15) NOT NULL AUTO_INCREMENT,
  nombre varchar(100) NOT NULL,
  link varchar(100) NOT NULL,
  orden int(2) NOT NULL,
  grupo int(2) NOT NULL,
  PRIMARY KEY (id),
  KEY id (id) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;

permission table:

CREATE TABLE IF NOT EXISTS permisos (
  id int(15) NOT NULL AUTO_INCREMENT,
  id_usaurio int(15) NOT NULL,
  id_menu int(15) NOT NULL,
  nuevo int(1) NOT NULL,
  editar int(1) NOT NULL,
  mostrar int(1) NOT NULL,
  borrar int(1) NOT NULL,
  pdf int(1) NOT NULL,
  excel int(1) NOT NULL,
  PRIMARY KEY (id),
  KEY id_menu (id_menu) USING BTREE,
  KEY id (id) USING BTREE,
  KEY permisos_ibfk_1 (id_usaurio) USING BTREE,
  CONSTRAINT permisos_ibfk_2 FOREIGN KEY (id_menu) REFERENCES menu (id) ON DELETE CASCADE ON UPDATE NO ACTION,
  CONSTRAINT permisos_ibfk_3 FOREIGN KEY (id_usaurio) REFERENCES agent (id) ON DELETE CASCADE ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=1696 DEFAULT CHARSET=utf8;

In the view:

       <ul class="nav">
        <li class="divider-vertical"></li>
          <?php 
          $data_gru = $rol->get_menu_grupo($_SESSION["credentials"]["userType"],$_SESSION["credentials"]["userId"]);
          foreach($data_gru as $valueg){
           ?>
          <li class="dropdown">
            <a data-toggle="dropdown" class="dropdown-toggle" href="#"><?php echo $valueg['nombre'] ?><b class="caret"></b></a>
            <ul class="dropdown-menu">
            <?php 
                $data_men = $rol->get_menu_link($_SESSION["credentials"]["userType"],$_SESSION["credentials"]["userId"],$valueg['grupo']);
                foreach($data_men as $value){
             ?>
              <li><a href="index.php?c=<?php echo $value['link']; ?>"><?php echo $value['nombre']; ?></a></li>
            <?php } ?>
            </ul>

In the model:

//Función donde extraemos el número de grupos del menú.
public function get_menu_grupo($tipo, $usuario){
    if($tipo == 1){
        $query = $this->db->query("SELECT menu.id, menu.nombre, menu.grupo FROM menu WHERE menu.link = '' Order By  menu.grupo ASC");   
    }else{
        $query = $this->db->query("SELECT menu.id, menu.nombre, menu.grupo FROM menu INNER JOIN permisos ON menu.id = permisos.id_menu WHERE menu.link = '' AND permisos.id_usaurio = '".$usuario."' GROUP BY menu.nombre Order By  menu.grupo ASC");
    }
    $this->aplicacion = '';
    while($list = mysqli_fetch_assoc($query)){
        $this->aplicacion[] = array_merge(array('nombre'=> $list['nombre']),array('grupo'=> $list['grupo']),array('id'=> $list['id']));
    }
    return $this->aplicacion;
}