diff --git a/ChangeLog b/ChangeLog
index e499c5b4e1c..b641ebf3ddb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -31,8 +31,8 @@ WARNING: Following changes may create regression for some external modules, but
 Dolibarr better:
 - Removed hoo supplierorderdao into supplier order creation. This is a business event, so we must use the 
   trigger ORDER_SUPPLIER_CREATE instead.
-- printLeftBlock is now compliant with hook development rules. It is an "addreplace" hook so you must 
-return content by doing ->resprints='mycontent' and not by doing return 'mycontent'  
+- Hooks 'printLeftBlock' and 'formConfirm' are now compliant with hook development rules. They are
+  "addreplace" hooks, so you must return content with "->resprints='mycontent'" and not with "return 'mycontent'"  
 
 
 ***** ChangeLog for 3.7 compared to 3.6.* *****
diff --git a/htdocs/comm/askpricesupplier/card.php b/htdocs/comm/askpricesupplier/card.php
index f2ca52f1f89..cbd0436e2ef 100644
--- a/htdocs/comm/askpricesupplier/card.php
+++ b/htdocs/comm/askpricesupplier/card.php
@@ -1346,9 +1346,9 @@ if ($action == 'create')
 
 	if (! $formconfirm) {
 		$parameters = array('lineid' => $lineid);
-		$formconfirm = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified
-			                                                                                         // by
-			                                                                                         // hook
+		$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+		if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+		elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 	}
 
 	// Print form confirm
diff --git a/htdocs/comm/propal.php b/htdocs/comm/propal.php
index de68313e6f8..c9d5170f7e6 100644
--- a/htdocs/comm/propal.php
+++ b/htdocs/comm/propal.php
@@ -1680,9 +1680,9 @@ if ($action == 'create')
 
 	if (! $formconfirm) {
 		$parameters = array('lineid' => $lineid);
-		$formconfirm = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified
-			                                                                                         // by
-			                                                                                         // hook
+		$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+		if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+		elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 	}
 
 	// Print form confirm
diff --git a/htdocs/commande/card.php b/htdocs/commande/card.php
index bef752f5954..aa72ec9bf68 100644
--- a/htdocs/commande/card.php
+++ b/htdocs/commande/card.php
@@ -253,7 +253,7 @@ if (empty($reshook))
 			$object->contactid = GETPOST('contactid');
 			$object->fk_incoterms = GETPOST('incoterm_id', 'int');
 			$object->location_incoterms = GETPOST('location_incoterms', 'alpha');
-			
+
 			// If creation from another object of another module (Example: origin=propal, originid=1)
 			if (! empty($origin) && ! empty($originid))
 			{
@@ -523,7 +523,7 @@ if (empty($reshook))
     {
     	$result = $object->setIncoterms(GETPOST('incoterm_id', 'int'), GETPOST('location_incoterms', 'alpha'));
     }
-	
+
 	// bank account
 	else if ($action == 'setbankaccount' && $user->rights->commande->creer) {
 	    $result=$object->setBankAccount(GETPOST('fk_account', 'int'));
@@ -1726,8 +1726,9 @@ if ($action == 'create' && $user->rights->commande->creer)
 
 		if (! $formconfirm) {
 			$parameters = array('lineid' => $lineid);
-			$formconfirm = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified
-			                                                                                    // by hook
+			$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+			if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+			elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 		}
 
 		// Print form confirm
@@ -1988,10 +1989,10 @@ if ($action == 'create' && $user->rights->commande->creer)
 			print '</td>';
 			print '</tr>';
 		}
-		
+
 		// Incoterms
 		if (!empty($conf->incoterm->enabled))
-		{			
+		{
 			print '<tr><td>';
 	        print '<table width="100%" class="nobordernopadding"><tr><td>';
 	        print $langs->trans('IncotermLabel');
@@ -2005,13 +2006,13 @@ if ($action == 'create' && $user->rights->commande->creer)
 			{
 				print $form->textwithpicto($object->display_incoterms(), $object->libelle_incoterms, 1);
 			}
-			else 
+			else
 			{
 				print $form->select_incoterms((!empty($object->fk_incoterms) ? $object->fk_incoterms : ''), (!empty($object->location_incoterms)?$object->location_incoterms:''), $_SERVER['PHP_SELF'].'?id='.$object->id);
 			}
 	        print '</td></tr>';
 		}
-	
+
 		// Other attributes
 		$cols = 3;
 		include DOL_DOCUMENT_ROOT . '/core/tpl/extrafields_view.tpl.php';
@@ -2243,10 +2244,10 @@ if ($action == 'create' && $user->rights->commande->creer)
 				}
 
 				// Cancel order
-				if ($object->statut == 1 && 
+				if ($object->statut == 1 &&
 				    ((empty($conf->global->MAIN_USE_ADVANCED_PERMS) && ! empty($user->rights->commande->cloturer))
 			       	|| (! empty($conf->global->MAIN_USE_ADVANCED_PERMS) && ! empty($user->rights->commande->order_advance->annuler)))
-				) 
+				)
 				{
 					print '<div class="inline-block divButAction"><a class="butActionDelete" href="' . $_SERVER["PHP_SELF"] . '?id=' . $object->id . '&amp;action=cancel">' . $langs->trans('Cancel') . '</a></div>';
 				}
diff --git a/htdocs/compta/facture.php b/htdocs/compta/facture.php
index d38519bf6d5..f87f797509b 100644
--- a/htdocs/compta/facture.php
+++ b/htdocs/compta/facture.php
@@ -324,7 +324,7 @@ if (empty($reshook))
     {
     	$result = $object->setIncoterms(GETPOST('incoterm_id', 'int'), GETPOST('location_incoterms', 'alpha'));
     }
-	
+
 	// bank account
 	else if ($action == 'setbankaccount' && $user->rights->facture->creer)
 	{
@@ -2289,7 +2289,7 @@ if ($action == 'create')
         print $form->select_incoterms((!empty($objectsrc->fk_incoterms) ? $objectsrc->fk_incoterms : ''), (!empty($objectsrc->location_incoterms)?$objectsrc->location_incoterms:''));
 		print '</td></tr>';
 	}
-	
+
 	// Other attributes
 	$parameters = array('objectsrc' => $objectsrc,'colspan' => ' colspan="3"');
 	$reshook = $hookmanager->executeHooks('formObjectOptions', $parameters, $object, $action); // Note that $action and $object may have been modified by
@@ -2749,8 +2749,9 @@ if ($action == 'create')
 
 	if (! $formconfirm) {
 		$parameters = array('lineid' => $lineid);
-		$formconfirm = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by
-		                                                                                    // hook
+		$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+		if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+		elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 	}
 
 	// Print form confirm
@@ -3389,10 +3390,10 @@ if ($action == 'create')
 		print '</td>';
 		print '</tr>';
 	}
-	
+
 	// Incoterms
 	if (!empty($conf->incoterm->enabled))
-	{			
+	{
 		print '<tr><td>';
         print '<table width="100%" class="nobordernopadding"><tr><td>';
         print $langs->trans('IncotermLabel');
@@ -3406,7 +3407,7 @@ if ($action == 'create')
 		{
 			print $form->textwithpicto($object->display_incoterms(), $object->libelle_incoterms, 1);
 		}
-		else 
+		else
 		{
 			print $form->select_incoterms((!empty($object->fk_incoterms) ? $object->fk_incoterms : ''), (!empty($object->location_incoterms)?$object->location_incoterms:''), $_SERVER['PHP_SELF'].'?id='.$object->id);
 		}
diff --git a/htdocs/fichinter/card.php b/htdocs/fichinter/card.php
index 661ffc9af30..9eb9b243830 100644
--- a/htdocs/fichinter/card.php
+++ b/htdocs/fichinter/card.php
@@ -1210,7 +1210,9 @@ else if ($id > 0 || ! empty($ref))
 	if (!$formconfirm)
 	{
 		$parameters=array('lineid'=>$lineid);
-		$formconfirm=$hookmanager->executeHooks('formConfirm',$parameters,$object,$action);    // Note that $action and $object may have been modified by hook
+		$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+		if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+		elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 	}
 
 	// Print form confirm
diff --git a/htdocs/fourn/commande/card.php b/htdocs/fourn/commande/card.php
index 41d06bebf43..3f6877d8d14 100644
--- a/htdocs/fourn/commande/card.php
+++ b/htdocs/fourn/commande/card.php
@@ -1733,7 +1733,9 @@ elseif (! empty($object->id))
 
 	if (!$formconfirm) {
 		$parameters=array('lineid'=>$lineid);
-		$formconfirm=$hookmanager->executeHooks('formConfirm',$parameters,$object,$action);    // Note that $action and $object may have been modified by hook
+		$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+		if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+		elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 	}
 
 	// Print form confirm
diff --git a/htdocs/fourn/facture/card.php b/htdocs/fourn/facture/card.php
index 1a37baa9937..cd6a9f64abd 100644
--- a/htdocs/fourn/facture/card.php
+++ b/htdocs/fourn/facture/card.php
@@ -1716,7 +1716,9 @@ else
 
         if (!$formconfirm) {
 			$parameters=array('lineid'=>$lineid);
-			$formconfirm=$hookmanager->executeHooks('formConfirm',$parameters,$object,$action);    // Note that $action and $object may have been modified by hook
+			$reshook = $hookmanager->executeHooks('formConfirm', $parameters, $object, $action); // Note that $action and $object may have been modified by hook
+			if (empty($reshook)) $formconfirm.=$hookmanager->resPrint;
+			elseif ($reshook > 0) $formconfirm=$hookmanager->resPrint;
 		}
 
 		// Print form confirm