Adds deprecation for non-string env values.

Author: Denis Brumann

configuration/environment_variables.rst

@@ -77,7 +77,7 @@ whenever the corresponding environment variable is *not* found:
 
         # config/services.yaml
         parameters:
-            env(DATABASE_HOST): localhost
+            env(DATABASE_HOST): 'localhost'
 
     .. code-block:: xml
 
@@ -97,6 +97,35 @@ whenever the corresponding environment variable is *not* found:
         // config/services.php
         $container->setParameter('env(DATABASE_HOST)', 'localhost');
 
+.. deprecated:: 4.3
+
+    Passing non-string values as default values for environment variables is no longer supported. Any non-string value,
+    e.g. an integer or float must be passed as string.
+
+    .. code-block:: yaml
+
+        # config/services.yaml
+        parameters:
+            env(DATABASE_PORT): '3306'
+
+    .. code-block:: xml
+
+        <!-- config/services.xml -->
+        <?xml version="1.0" encoding="UTF-8" ?>
+        <container xmlns="http://symfony.com/schema/dic/services"
+            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+            xsi:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
+
+            <parameters>
+                <parameter key="env(DATABASE_PORT)">3306</parameter>
+            </parameters>
+         </container>
+
+    .. code-block:: php
+
+        // config/services.php
+        $container->setParameter('env(DATABASE_PORT)', '3306');
+
 .. _configuration-env-var-in-prod:
 
 Configuring Environment Variables in Production