Add example

git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@37167 c90b9560-bf6c-de11-be94-00142212c4b1

functions/gmp.xml

@@ -33,6 +33,25 @@
    every function that expects GMP number. See also
    <function>gmp_init</function> function.
    </para></note>
+   <para>
+		<example>
+		<title>Factorial function using GMP</title>
+		<programlisting role="php">
+&lt;?php
+function fact($x) {
+  if($x <= 1) 
+        return 1;
+  else
+        return gmp_mul($x,fact($x-1));
+}
+
+print gmp_strval(fact(1000))."\n";
+?>
+		</programlisting>
+		</example>
+		This will calculate factiorial of 1000 (pretty big number)
+		very fast.
+	</para>
  </partintro>
 
   <refentry id="function.gmp-init">