Mark depencendy of PHP mode on HTMLMixed

mode/php/index.html

@@ -44,7 +44,7 @@ function hello($who) {
 
     <p>Simple HTML/PHP mode based on
     the <a href="../clike/">C-like</a> mode. Depends on XML,
-    JavaScript, CSS, and C-like modes.</p>
+    JavaScript, CSS, HTMLMixed, and C-like modes.</p>
 
     <p><strong>MIME types defined:</strong> <code>application/x-httpd-php</code> (HTML with PHP code), <code>text/x-php</code> (plain, non-wrapped PHP code).</p>
   </body>