Checking Var's passed via URL

Suppose the following code that will be used in 3 different urls calls <?php if (isset($_GET['modo'])){ echo "modo seted<BR>"; } else { echo "modo unseted<BR>"; } if (isset($_GET['key'])) { echo "key seted<BR>"; } else { echo "key unseted<BR>"; } ?> If I call with the following url http://mydomain/Cliente.php?modo=1&key=3741 I receive the following result modo seted key seted When calling with http://mydomain/Cliente.php?key=3741 I receive modo unseted key seted And when I use http://mydomain/Cliente.php?modo=1 I get this message Parse error: parse error, unexpected T_ISSET, expecting '(' in http://mydomain/Cliente.php on line 2 I'm expecting the following return modo seted key unseted What am'I doing wrong ?