diff --git a/reference/xsl/xsltprocessor/registerphpfunctions.xml b/reference/xsl/xsltprocessor/registerphpfunctions.xml
index adb53a29ab41..c04d5b46239c 100644
--- a/reference/xsl/xsltprocessor/registerphpfunctions.xml
+++ b/reference/xsl/xsltprocessor/registerphpfunctions.xml
@@ -11,10 +11,17 @@
    <modifier>public</modifier> <type>void</type><methodname>XSLTProcessor::registerPHPFunctions</methodname>
    <methodparam choice="opt"><type class="union"><type>array</type><type>string</type><type>null</type></type><parameter>functions</parameter><initializer>&null;</initializer></methodparam>
   </methodsynopsis>
-  <para>
+  <simpara>
    This method enables the ability to use PHP functions as XSLT functions
    within XSL stylesheets.
-  </para>
+  </simpara>
+  <warning>
+    <simpara>
+      <parameter>functions</parameter> defaults to &null;, meaning that by
+      default calling this method enables access to <emphasis>all</emphasis>
+      PHP functions.
+    </simpara>
+  </warning>
  </refsect1>
  <refsect1 role="parameters">
   &reftitle.parameters;
@@ -23,17 +30,18 @@
     <varlistentry>
      <term><parameter>functions</parameter></term>
      <listitem>
-      <para>
+      <simpara>
        Use this parameter to only allow certain functions to be called from 
        XSLT.
-      </para>
-      <para>
+      </simpara>
+      <simpara>
        This parameter can be one of the following:
+       &null; to indicate that all functions are allowed,
        a <type>string</type> (a function name),
        an indexed <type>array</type> of function names,
        or an associative <type>array</type> with keys being the function name
        and the associated value being the <type>callable</type>.
-      </para>
+      </simpara>
      </listitem>
     </varlistentry>
    </variablelist>
@@ -44,9 +52,9 @@
 
  <refsect1 role="returnvalues">
   &reftitle.returnvalues;
-  <para>
+  <simpara>
    &return.void;
-  </para>
+  </simpara>
  </refsect1>
 
  <refsect1 role="changelog">