add must-revalidate flag to Cache-Control header

Author: dhoffend

src/Cache.php

@@ -22,16 +22,25 @@ class Cache
      */
     protected $maxAge;
 
+    /**
+     * Cache-Control includes must-revalidate flag
+     *
+     * @var bool
+     */
+    protected $mustRevalidate;
+
     /**
      * Create new HTTP cache
      *
-     * @param string $type   The cache type: "public" or "private"
-     * @param int    $maxAge The maximum age of client-side cache
+     * @param string $type           The cache type: "public" or "private"
+     * @param int    $maxAge         The maximum age of client-side cache
+     * @param bool   $mustRevalidate must-revalidate
      */
-    public function __construct($type = 'private', $maxAge = 86400)
+    public function __construct($type = 'private', $maxAge = 86400, $mustRevalidate = false)
     {
         $this->type = $type;
         $this->maxAge = $maxAge;
+        $this->mustRevalidate = $mustRevalidate;
     }
 
     /**
@@ -50,9 +59,10 @@ public function __invoke(RequestInterface $request, ResponseInterface $response,
         // Cache-Control header
         if (!$response->hasHeader('Cache-Control')) {
             $response = $response->withHeader('Cache-Control', sprintf(
-                '%s, max-age=%s',
+                '%s, max-age=%s%s',
                 $this->type,
-                $this->maxAge
+                $this->maxAge,
+                $this->mustRevalidate ? ', must-revalidate' : ''
             ));
         }
 

src/CacheProvider.php

@@ -21,14 +21,15 @@ public function register(Container $container)
     /**
      * Enable client-side HTTP caching
      *
-     * @param  ResponseInterface $response PSR7 response object
-     * @param  string            $type     Cache-Control type: "private" or "public"
-     * @param  null|int|string   $maxAge   Maximum cache age (integer timestamp or datetime string)
+     * @param  ResponseInterface $response       PSR7 response object
+     * @param  string            $type           Cache-Control type: "private" or "public"
+     * @param  null|int|string   $maxAge         Maximum cache age (integer timestamp or datetime string)
+     * @param  bool              $mustRevalidate add option "must-revalidate" to Cache-Control
      *
      * @return ResponseInterface           A new PSR7 response object with `Cache-Control` header
      * @throws InvalidArgumentException if the cache-control type is invalid
      */
-    public function allowCache(ResponseInterface $response, $type = 'private', $maxAge = null)
+    public function allowCache(ResponseInterface $response, $type = 'private', $maxAge = null, $mustRevalidate = false)
     {
         if (!in_array($type, ['private', 'public'])) {
             throw new InvalidArgumentException('Invalid Cache-Control type. Must be "public" or "private".');
@@ -41,6 +42,10 @@ public function allowCache(ResponseInterface $response, $type = 'private', $maxA
             $headerValue = $headerValue . ', max-age=' . $maxAge;
         }
 
+        if ($mustRevalidate) {
+            $headerValue = $headerValue . ", must-revalidate";
+        }
+
         return $response->withHeader('Cache-Control', $headerValue);
     }