diff --git a/app/tuto1/index.php b/app/tuto1/index.php
index 732a691cd72dc726c671124970c2a0da4627b436..5f0f92f41c445bdca3f3215fe838e70dc434810e 100644
--- a/app/tuto1/index.php
+++ b/app/tuto1/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto2/index.php b/app/tuto2/index.php
index 3d3001617ecefc201b94bd4e154e365b73ad6d74..7a40f46be763f1a787c6a5ed1142bfa25815dea2 100644
--- a/app/tuto2/index.php
+++ b/app/tuto2/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto3-1/index.php b/app/tuto3-1/index.php
index c8c9ecba375eaa97cc991360cf684ecd6a3f35ea..f5ce6ad54d440e84fa064eb55001f491f7ff17b0 100644
--- a/app/tuto3-1/index.php
+++ b/app/tuto3-1/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto3-2/index.php b/app/tuto3-2/index.php
index 10fed6de2474f33a13e1c8f6304bf86b993848f0..c98ed8c60eae9923e0a8bfa8dd7e159f9758fe5c 100644
--- a/app/tuto3-2/index.php
+++ b/app/tuto3-2/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto3-3/index.php b/app/tuto3-3/index.php
index ae661cac0a92c97979f57b94ce50a29ef42063d3..bed67355965ccff900e3f69bc53a0c6da396f3c9 100644
--- a/app/tuto3-3/index.php
+++ b/app/tuto3-3/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto3-4/index.php b/app/tuto3-4/index.php
index abed35ed75a8cf86facf451e213f636754d92fd1..3ad67a512962a7780680c692fd86b06607e5a41b 100644
--- a/app/tuto3-4/index.php
+++ b/app/tuto3-4/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto3-ai4t/index.php b/app/tuto3-ai4t/index.php
index 738c1397e1b8cba722a254f94f3f31c0916a02f1..789e5279546fe08bb894b3d0e45b54bba26db797 100644
--- a/app/tuto3-ai4t/index.php
+++ b/app/tuto3-ai4t/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 
 ?>
 
diff --git a/app/tuto3/index.php b/app/tuto3/index.php
index bd6c740ed30ac528f805db3b207d50c77e61cc1c..8ab34ac0e1908d4883d346b5c5dc2b3e0b0239df 100644
--- a/app/tuto3/index.php
+++ b/app/tuto3/index.php
@@ -2,7 +2,7 @@
 
 $currentURL = $_SERVER['REQUEST_URI'];
 $tutoURL = substr($currentURL, 0, strpos($currentURL, 'app/') - 1);
-$lang = $_GET['lang'] ?: 'fr';
+$lang = isset($_GET['lang']) ? $_GET['lang'] : 'fr';
 $arrayPages=explode("?",$currentURL);
 //var_dump($arrayPages);
 if(count($arrayPages)==2){