Add a flag to keep the custom ttl header (#504)

Author: alexander-schranz

src/SymfonyCache/CustomTtlListener.php

@@ -30,6 +30,11 @@ class CustomTtlListener implements EventSubscriberInterface
      */
     private $ttlHeader;
 
+    /**
+     * @var bool
+     */
+    private $keepTtlHeader;
+
     /**
      * Header used for backing up the s-maxage.
      *
@@ -38,11 +43,13 @@ class CustomTtlListener implements EventSubscriberInterface
     public const SMAXAGE_BACKUP = 'FOS-Smaxage-Backup';
 
     /**
-     * @param string $ttlHeader The header that is used to specify the TTL header
+     * @param string $ttlHeader     The header name that is used to specify the time to live
+     * @param bool   $keepTtlHeader Keep the custom TTL header on the response for later usage (e.g. debugging)
      */
-    public function __construct($ttlHeader = 'X-Reverse-Proxy-TTL')
+    public function __construct($ttlHeader = 'X-Reverse-Proxy-TTL', $keepTtlHeader = false)
     {
         $this->ttlHeader = $ttlHeader;
+        $this->keepTtlHeader = $keepTtlHeader;
     }
 
     /**
@@ -85,7 +92,10 @@ public function cleanResponse(CacheEvent $e)
                 $response->headers->addCacheControlDirective('s-maxage', $smaxage);
             }
         }
-        $response->headers->remove($this->ttlHeader);
+
+        if (!$this->keepTtlHeader) {
+            $response->headers->remove($this->ttlHeader);
+        }
         $response->headers->remove(static::SMAXAGE_BACKUP);
     }