More examples and tweaks

* Signal dispatch() method now uses own pid as default value
* SharedData now updates checksum cache on set()

src/Shm/SharedData.php

@@ -113,6 +113,7 @@ class SharedData extends SharedMemory
 
         // Update the data
         $this[self::IDX_DATA + $index] = [ md5($value), $value ];
+        $this->checks[$key] = md5($value);
         $this->unlock();
         return true;
     }