if (strpos($_SERVER['REQUEST_URI'], "online") >= 0) {
    $left_col_class = "gkPageContent";
}
elseif(strpos($_SERVER['REQUEST_URI'], "student-login") >= 0)  {
    $left_col_class = "showme";
    echo "this is not sanjay";
}
elseif(strpos($_SERVER['REQUEST_URI'], "my-account/orders") >= 0)  {
    $left_col_class = "showme";
}
elseif(strpos($_SERVER['REQUEST_URI'], "my-account/my-courses") >= 0)  {
    $left_col_class = "showme";
}
elseif(strpos($_SERVER['REQUEST_URI'], "my-account/fourm") >= 0)  {
    $left_col_class = "showme";
}
elseif(strpos($_SERVER['REQUEST_URI'], "student-login") >= 0)  {
    $left_col_class = "showme";
}
elseif (strpos($_SERVER['REQUEST_URI'], "student-login") >= 0)  {
    $left_col_class = "showme";
}
else{
    echo "dam thing";
}

echo $left_col_class;

$lookup = array(
              'online' => 'gkPageContent',
              'student-login' => 'showme',
              'my-account/orders' => 'showme',
              'my-account/my-courses' => 'showme',
              'my-account/fourm' => 'showme'       // check your spelling
          );

if (isset($lookup[$_SERVER['REQUEST_URI']])) {
    $left_col_class = $lookup[$_SERVER['REQUEST_URI']];
} else {
    $left_col_class = $default_fallback_value; // ..."darn thing" would be unhelpful, me thinks
}