Found how to store UsersIn :)

inc/Invoices.class.php

@@ -1,13 +1,13 @@
 <?php
-    // TODO : Handle users_in
     require_once('data/config.php');
     require_once('Storage.class.php');
+    require_once('UsersIn.class.php');
 
     class Invoice extends Storage {
-        protected $id = 0, $date, $users_in, $guests, $buyer, $amount, $what;
+        protected $id = 0, $date, $users_in, $buyer, $amount, $what;
         // date is a DateTime object
         // buyer is a User object
-        // guests is an array with same keys as users_in
+        // users_in is a UsersIn objects
         protected $TABLE_NAME = "Invoices";
         protected $fields = array(
             'id'=>'key',
@@ -19,6 +19,7 @@
 
         public function __construct() {
             parent::__construct();
+            $users_in = new UsersIn();
         }
 
         // Getters
@@ -39,6 +40,10 @@
             return $this->buyer;
         }
 
+        public function getUsersIn() {
+            return $this->users_in;
+        }
+
         public function getAmount() {
             return $this->amount;
         }
@@ -50,6 +55,7 @@
         // Setters
         // =======
         public function setId($id) {
+            $this->users_in->setId($id);
             $this->id = (int) $id;
         }
 
@@ -75,6 +81,11 @@
             $this->what = $what;
         }
 
+        public function setUsersIn($users_in) {
+            // Note : users_in in param is an array with users in listed and guests for each user
+            $this->users_in->set($users_in);
+        }
+
         // Maps htmlspecialchars on the class before display
         // =================================================
         public function secureDisplay() {

inc/UsersIn.class.php

@@ -0,0 +1,63 @@
+<?php
+    //TODO : load() and save() overload
+    require_once('data/config.php');
+    require_once('Storage.class.php');
+
+    class UsersIn extends Storage {
+        protected $invoice_id = 0, $users_list;
+        //users_list is an array of users_id and number of guest per user
+        protected $TABLE_NAME = "Users_in";
+        protected $fields = array(
+            'invoice_id'=>'int',
+            'user_id'=>'int',
+            'guests'=>'int'
+            );
+
+        public function __construct() {
+            parent::__construct();
+            $users_list = array();
+        }
+
+        // Getters
+        // =======
+        public function getInvoiceId() {
+            return $this->invoice_id;
+        }
+
+        public function get() {
+            return $this->users_list;
+        }
+
+        // Setters
+        // =======
+        public function setInvoiceId($id) {
+            $this->invoice_id = (int) $id;
+        }
+
+        public function set($users_in) {
+            $this->users_list = $users_in;
+        }
+
+        // Maps htmlspecialchars on the class before display
+        // =================================================
+        public function secureDisplay() {
+            $this->invoice_id = (int) $this->invoice_id;
+
+            $temp_array = array();
+            foreach($this->users_list as $user=>$guests) {
+                $temp_array[(int) $user] = (int) $guests;
+            }
+            $this->users_in = $temp_array;
+
+            return $this;
+        }
+
+        // Restores object from array
+        // ==========================
+        public function sessionRestore($data, $serialized = false) { 
+            // TODO ***
+            if($serialized) {
+                $data = unserialize($data);
+            }
+        }
+    }