[12.x] Fix type casting for environment variables in config files (#6637)

* Update app.php

* Update cache.php

* Update database.php

* Update logging.php

* Update mail.php

config/app.php

@@ -101,7 +101,7 @@ return [
 
     'previous_keys' => [
         ...array_filter(
-            explode(',', env('APP_PREVIOUS_KEYS', ''))
+            explode(',', (string) env('APP_PREVIOUS_KEYS', ''))
         ),
     ],
 

config/cache.php

@@ -103,6 +103,6 @@ return [
     |
     */
 
-    'prefix' => env('CACHE_PREFIX', Str::slug(env('APP_NAME', 'laravel')).'-cache-'),
+    'prefix' => env('CACHE_PREFIX', Str::slug((string) env('APP_NAME', 'laravel')).'-cache-'),
 
 ];

config/database.php

@@ -147,7 +147,7 @@ return [
 
         'options' => [
             'cluster' => env('REDIS_CLUSTER', 'redis'),
-            'prefix' => env('REDIS_PREFIX', Str::slug(env('APP_NAME', 'laravel')).'-database-'),
+            'prefix' => env('REDIS_PREFIX', Str::slug((string) env('APP_NAME', 'laravel')).'-database-'),
             'persistent' => env('REDIS_PERSISTENT', false),
         ],
 

config/logging.php

@@ -54,7 +54,7 @@ return [
 
         'stack' => [
             'driver' => 'stack',
-            'channels' => explode(',', env('LOG_STACK', 'single')),
+            'channels' => explode(',', (string) env('LOG_STACK', 'single')),
             'ignore_exceptions' => false,
         ],
 

config/mail.php

@@ -46,7 +46,7 @@ return [
             'username' => env('MAIL_USERNAME'),
             'password' => env('MAIL_PASSWORD'),
             'timeout' => null,
-            'local_domain' => env('MAIL_EHLO_DOMAIN', parse_url(env('APP_URL', 'http://localhost'), PHP_URL_HOST)),
+            'local_domain' => env('MAIL_EHLO_DOMAIN', parse_url((string) env('APP_URL', 'http://localhost'), PHP_URL_HOST)),
         ],
 
         'ses' => [