Um.. yeah. Just.. reverse the order of the code.
viewSearch();
function fnSearchResults() {
echo "RESULTS";
}
function viewSearch() {
echo "<form method=\"post\" action=\"".$_SERVER['PHP_SELF']."\">\n";
echo "<input type=\"submit\" name=\"searchNow\" class=\"btn\" value=\"Search Now\">";
}
if (isset($_POST['searchNow'])) {fnSearchResults();}