add html_escape() function to escape HTML.
diff --git a/user_guide/general/common_functions.html b/user_guide/general/common_functions.html
index 6545775..7cff632 100644
--- a/user_guide/general/common_functions.html
+++ b/user_guide/general/common_functions.html
@@ -104,6 +104,8 @@
<p>This function prevents inserting null characters between ascii characters, like Java\0script.</p>
+<h2>html_escape(<var>$mixed</var>)</h2>
+<p>This function provides short cut for htmlspecialchars() function. It accepts string and array. To prevent Cross Site Scripting (XSS), it is very useful.</p>
</div>