diff --git a/user_guide/changelog.html b/user_guide/changelog.html
index 7bf5028..1de9eff 100644
--- a/user_guide/changelog.html
+++ b/user_guide/changelog.html
@@ -92,6 +92,7 @@
 			<li>Modified <a href="general/errors.html">show_error()</a> to allow sending of HTTP server response codes.</li>
 			<li>Modified <a href="general/errors.html">show_404()</a> to send 404 status code, removing non-CGI compatible header() statement from error_404.php template.</li>
 			<li>Added set_status_header() to the <a href="general/common_functions.html">Common functions<a> to allow use when the Output class is unavailable.</li>
+			<li>Added is_php() to <a href="general/common_functions.html">Common functions</a> to facilitate PHP version comparisons.</p> 
 		</ul>
 	</li>
 </ul>
diff --git a/user_guide/general/common_functions.html b/user_guide/general/common_functions.html
index 980a5a9..1f43944 100644
--- a/user_guide/general/common_functions.html
+++ b/user_guide/general/common_functions.html
@@ -59,6 +59,18 @@
 
 <p>CodeIgniter uses a few functions for its operation that are globally defined, and are available to you at any point. These do not require loading any libraries or helpers.</p>
 
+<h2>is_php('<var>version_number</var>')</h2>
+
+<p>is_php() determines of the PHP version being used is greater than the supplied <var>version_number</var>.</p>
+
+<code>if (is_php('5.3.0'))<br />
+{<br />
+&nbsp;&nbsp;&nbsp;&nbsp;$str = quoted_printable_encode($str);<br />
+}</code>
+
+<p>Returns boolean <kbd>TRUE</kbd> if the installed version of PHP is equal to or greater than the supplied version number.  Returns  <kbd>FALSE</kbd> if the installed version of PHP is lower than the supplied version number.</p>
+
+
 <h2>is_really_writable('<var>path/to/file</var>')</h2>
 
 <p>is_writable() returns TRUE on Windows servers when you really can't write to the file as the OS reports to PHP as FALSE only if the read-only attribute is marked. This function determines if a file is actually writable by attempting to write to it first. Generally only recommended on platforms where this information may be unreliable.</p>