documentation fix

Author: EmielBruijntjes

documentation/output-and-errors.html

@@ -24,7 +24,7 @@ <h1>Output and errors</h1>
     Php::out is a regular std::ostream object. This has as consequence that 
     it uses an internal buffer that needs to be flushed. This flushing
     occurs automatically when you add 'std::endl' to the output, or when you 
-    add 'std::sync' explicitly.
+    add 'std::flush' explicitly.
 </p>
 <p>
 <pre class="language-c++"><code>