diff --git a/.gitignore b/.gitignore
index 1a287623d0..f42daa1ca0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,3 +59,4 @@ composer.lock
 /node_modules/
 libraries/cache/
 js/dist/
+/setup/styles.css.map
diff --git a/ChangeLog b/ChangeLog
index f42f003ade..0e917f0662 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,9 @@
 phpMyAdmin - ChangeLog
 ======================
 
+4.9.9 (not yet released)
+- issue #17305 Fix syntax error for PHP 5
+
 4.9.8 (2022-01-20)
 - issue #14321 Display a correct error page when "$cfg['Servers'][$i]['SignonURL']" is empty for auth_type=signon
 - issue #14321 [security] Remove leaked HTML on signon page redirect before login for auth_type=signon
diff --git a/composer.json b/composer.json
index d5c178e0ee..11ab5e9a98 100644
--- a/composer.json
+++ b/composer.json
@@ -102,5 +102,12 @@
             "phpcs",
             "phpunit --color=always"
         ]
+    },
+    "config": {
+        "allow-plugins": {
+            "dealerdirect/phpcodesniffer-composer-installer": true,
+            "phpstan/extension-installer": true,
+            "composer/package-versions-deprecated": true
+        }
     }
 }
diff --git a/libraries/classes/DatabaseInterface.php b/libraries/classes/DatabaseInterface.php
index 7ab5d754fb..0edc297cd3 100644
--- a/libraries/classes/DatabaseInterface.php
+++ b/libraries/classes/DatabaseInterface.php
@@ -1563,7 +1563,7 @@ class DatabaseInterface
      */
     public function initRelationParamsCache()
     {
-        $storageDbName = $GLOBALS['cfg']['Server']['pmadb'] ?? '';
+        $storageDbName = isset($GLOBALS['cfg']['Server']['pmadb']) ? $GLOBALS['cfg']['Server']['pmadb'] : '';
         // Use "phpmyadmin" as a default database name to check to keep the behavior consistent
         $storageDbName = $storageDbName !== null
                             && is_string($storageDbName)
@@ -1574,7 +1574,7 @@ class DatabaseInterface
         $this->relation->fixPmaTables($storageDbName, false);
 
         // This global will be changed if fixPmaTables did find one valid table
-        $storageDbName = $GLOBALS['cfg']['Server']['pmadb'] ?? '';
+        $storageDbName = isset($GLOBALS['cfg']['Server']['pmadb']) ? $GLOBALS['cfg']['Server']['pmadb'] : '';
 
         // Empty means that until now no pmadb was found eligible
         if (empty($storageDbName)) {