diff --git a/_routes.php b/_routes.php
index 2eb30ec..ac9274d 100644
--- a/_routes.php
+++ b/_routes.php
@@ -261,70 +261,84 @@ $this->post(
             ) {
                 $real_contrib = true;
             }
-
-            //we'll now try to add the relevant cotisation
-            if ($post['payment_status'] == 'Completed') {
-                /**
-                * We will use the following parameters:
-                * - mc_gross: the amount
-                * - custom: member id
-                * - item_number: contribution type id
-                *
-                * If no member id is provided, we only send to post contribution
-                * script, Galette does not handle anonymous contributions
-                */
-                $args = array(
-                    'type'          => $post['item_number'],
-                    'adh'           => $post['custom'],
-                    'payment_type'  => PaymentType::PAYPAL
-                );
-                if ($this->preferences->pref_membership_ext != '') {
-                    $args['ext'] = $this->preferences->pref_membership_ext;
-                }
-                $contrib = new Contribution($this->zdb, $this->login, $args);
-                $contrib->amount = $post['mc_gross'];
-
-                //all goes well, we can proceed
-                if ($contrib->isCotis() && $real_contrib) {
-                    // Check that membership fees does not overlap
-                    $overlap = $contrib->checkOverlap();
-                    if ($overlap !== true) {
-                        if ($overlap === false) {
+            
+            if ($ph->isProcessed($post))
+            {
+                $ph->setState('already');
+                Analog::log(
+                    'A paypal payment notification has been received, but it is already processed!',
+                    Analog::WARNING
+                    );
+            }
+            else
+            {
+                //we'll now try to add the relevant cotisation
+                if ($post['payment_status'] == 'Completed') {
+                    /**
+                    * We will use the following parameters:
+                    * - mc_gross: the amount
+                    * - custom: member id
+                    * - item_number: contribution type id
+                    *
+                    * If no member id is provided, we only send to post contribution
+                    * script, Galette does not handle anonymous contributions
+                    */
+                    $args = array(
+                        'type'          => $post['item_number'],
+                        'adh'           => $post['custom'],
+                        'payment_type'  => PaymentType::PAYPAL
+                    );
+                    if ($this->preferences->pref_membership_ext != '') {
+                        $args['ext'] = $this->preferences->pref_membership_ext;
+                    }
+                    $contrib = new Contribution($this->zdb, $this->login, $args);
+                    $contrib->amount = $post['mc_gross'];
+    
+                    //all goes well, we can proceed
+                    if ($contrib->isCotis() && $real_contrib) {
+                        // Check that membership fees does not overlap
+                        $overlap = $contrib->checkOverlap();
+                        if ($overlap !== true) {
+                            if ($overlap === false) {
+                                Analog::log(
+                                    'An eror occured checking overlaping fees :(',
+                                    Analog::ERROR
+                                );
+                            } else {
+                                //method directly return error message
+                                Analog::log(
+                                    'Error while calculating overlaping fees from paypal payment: ' . $overlap,
+                                    Analog::ERROR
+                                );
+                            }
+                        }
+                    }
+    
+                    if ($real_contrib) {
+                        $store = $contrib->store();
+                        if ($store === true) {
+                            $ph->setState('processed');
+                            //contribution has been stored :)
                             Analog::log(
-                                'An eror occured checking overlaping fees :(',
-                                Analog::ERROR
+                                'Paypal payment has been successfully registered as a contribution',
+                                Analog::INFO
                             );
                         } else {
-                            //method directly return error message
+                            //something went wrong :'(
+                            $ph->setState('errorstoring');
                             Analog::log(
-                                'Error while calculating overlaping fees from paypal payment: ' . $overlap,
+                                'An error occured while storing a new contribution from Paypal payment',
                                 Analog::ERROR
                             );
                         }
                     }
+                } else {
+                    $ph->setState('notcompleted');
+                    Analog::log(
+                        'A paypal payment notification has been received, but is not completed!',
+                        Analog::WARNING
+                    );
                 }
-
-                if ($real_contrib) {
-                    $store = $contrib->store();
-                    if ($store === true) {
-                        //contribution has been stored :)
-                        Analog::log(
-                            'Paypal payment has been successfully registered as a contribution',
-                            Analog::INFO
-                        );
-                    } else {
-                        //something went wrong :'(
-                        Analog::log(
-                            'An error occured while storing a new contribution from Paypal payment',
-                            Analog::ERROR
-                        );
-                    }
-                }
-            } else {
-                Analog::log(
-                    'A paypal payment notification has been received, but is not completed!',
-                    Analog::WARNING
-                );
             }
         } else {
             Analog::log(
diff --git a/lib/GalettePaypal/PaypalHistory.php b/lib/GalettePaypal/PaypalHistory.php
index 0cab2b7..c2b2810 100644
--- a/lib/GalettePaypal/PaypalHistory.php
+++ b/lib/GalettePaypal/PaypalHistory.php
@@ -63,6 +63,8 @@ class PaypalHistory extends History
     public const TABLE = 'history';
     public const PK = 'id_paypal';
 
+    private $_id;
+    
     protected $_types = array(
         'text',
         'date',
@@ -110,13 +112,18 @@ class PaypalHistory extends History
                 'history_date'  => date('Y-m-d H:i:s'),
                 'amount'        => $request['mc_gross'],
                 'comments'      => $request['item_name'],
-                'request'       => serialize($request)
+                'request'       => serialize($request),
+                'signature'   => $request['verify_sign'], 
+                'state'         => ''  
             );
+            //ALTER TABLE `galetteT1_paypal_history` ADD `signature` VARCHAR(255) NOT NULL AFTER `id_paypal`;
+            //ALTER TABLE `galetteT1_paypal_history` ADD `state` VARCHAR(20) NOT NULL AFTER `signature`;
 
             $insert = $this->zdb->insert($this->getTableName());
             $insert->values($values);
             $this->zdb->execute($insert);
-
+            $this->_id = $this->zdb->driver->getLastGeneratedValue();
+            
             Analog::log(
                 'An entry has been added in paypal history',
                 Analog::INFO
@@ -216,4 +223,32 @@ class PaypalHistory extends History
 
         return $order;
     }
+    
+    public function isProcessed($request)
+    {
+        $select = $this->zdb->select($this->getTableName());
+        $select->where([
+            'signature' => $request['verify_sign'], 
+            'state' => 'processed'
+            ]);
+        $results = $this->zdb->execute($select);
+        return count($results)>0;
+    }
+  
+    public function setState($state)
+    {
+        try {
+            $update = $this->zdb->update($this->getTableName());
+            $update->set(['state' => $state])
+                    ->where(['id_paypal' => $this->_id]);
+            $this->zdb->execute($update); 
+        }
+        catch (\Exception $e) {
+            Analog::log(
+                'An error occurred when updating state field | ' . $e->getMessage(),
+                Analog::ERROR
+                );
+        }
+    }
+        
 }