do not override config when intl is not installed

framework/CHANGELOG.md

@@ -4,6 +4,7 @@ Yii Framework 2 Change Log
 2.0.0 under development
 -----------------------
 
+- Bug #5260: `yii\i18n\Formatter::decimalSeparator` and `yii\i18n\Formatter::thousandSeparator` where not configurable when intl is not installed (execut, cebe)
 - Bug: Date and time formatting now assumes UTC as the timezone for input dates unless a timezone is explicitly given (cebe)
 - Enh #4275: Added `removeChildren()` to `yii\rbac\ManagerInterface` and implementations (samdark)
 

framework/i18n/Formatter.php

@@ -208,8 +208,12 @@ class Formatter extends Component
         }
         $this->_intlLoaded = extension_loaded('intl');
         if (!$this->_intlLoaded) {
-            $this->decimalSeparator = '.';
-            $this->thousandSeparator = ',';
+            if ($this->decimalSeparator === null) {
+                $this->decimalSeparator = '.';
+            }
+            if ($this->thousandSeparator === null) {
+                $this->thousandSeparator = ',';
+            }
         }
     }