Identifier for mixed data and cache hit handling

- Adds new function to create identifier of mixed data
- Allowes mixed data "with" cache
- Caches only if not already cached
- Touch cached files on use to handle cache item hit

src/Cache.php

@@ -33,7 +33,7 @@ public function wrap($func)
     return function() use ($func)
     {
       $arguments = func_get_args();
-      $identifier = sha1(serialize($arguments));
+      $identifier = $this->identifierOf($arguments);
 
       return $this->get($identifier) ?:
         $this->set($identifier,
@@ -45,14 +45,30 @@ public function wrap($func)
 
   /**
    * @param callback $func
-   * @param string $identifier
+   * @param string|mixed $identifier
    * @return mixed
    */
   public function with($func, $identifier) {
+    $identifier = is_string($identifier) ? 
+      $identifier : 
+      $this->identifierOf($identifier);
+
     $cachedValue = $this->get($identifier, null);
+    $alreadyCached = null !== $cachedValue;
     $funcResult = call_user_func($func, $cachedValue);
-    $this->set($identifier, $cachedValue);
+
+    if(false === $alreadyCached) {
+      $this->set($identifier, $cachedValue);
+    }
 
     return $funcResult;
   }
+
+  /**
+   * @param mixed $data
+   * @return string
+   */
+  public function identifierOf($data) {
+    return sha1(serialize($data));
+  }
 }

src/FileCache.php

@@ -33,27 +33,31 @@ public function __destruct()
 
   /**
    * @param string $identifier
-   * @param mixed $default
-   * @return mixed
+   * @return boolean
    */
-  public function get($identifier, $default = null)
+  public function has($identifier)
   {
-    return $this->inMemory->get($identifier, null) ?:
-      $this->inMemory->set($identifier, 
-        (unserialize(
-          file_get_contents(
-            $this->determineItemPath($identifier))) ?:
-        $default));
+    return $this->inMemory->has($identifier) || 
+           file_exists($this->determineItemPath($identifier));
   }
 
   /**
    * @param string $identifier
-   * @return boolean
+   * @param mixed $default
+   * @return mixed
    */
-  public function has($identifier)
+  public function get($identifier, $default = null)
   {
-    return $this->inMemory->has($identifier) || 
-           file_exists($this->determineItemPath($identifier));
+    $filepath = $this->determineItemPath($identifier);
+
+    $cached = $this->inMemory->get($identifier, null) ?:
+      $this->inMemory->set($identifier, 
+        (unserialize(
+          file_get_contents($filepath)) ?:
+        $default));
+
+    touch($filepath);
+    return $cached;
   }
 
   /**