$valid_signal = false;
 if ($_GET["railway:signal:main"] == "DE-ESO:hp") {
     if (isset($_GET["railway:signal:main:form"])) {
         if ($_GET["railway:signal:main:form"] == "light") {
             $result = HV_main_light::generateImage($height);
             $valid_signal = true;
         } elseif ($_GET["railway:signal:main:form"] == "semaphore") {
             $result = HV_main_semaphore::generateImage($height);
             $valid_signal = true;
         }
     }
 } elseif ($_GET["railway:signal:main"] == "DE-ESO:ks") {
     $result = KS_main::generateImage($height);
     $valid_signal = true;
 } elseif ($_GET["railway:signal:main"] == "DE-ESO:hl") {
     $result = HL_main::generateImage($height);
     $valid_signal = true;
 } else {
     if ($_GET["railway:signal:main:form"] == "semaphore") {
         $result = Main_semaphore::generateImage($height);
         $valid_signal = true;
     } else {
         $result = Main_light::generateImage($height);
         $valid_signal = true;
     }
 }
 if ($valid_signal) {
     $signal[$s] = $result[0];
     $height += $result[1];
     $s++;
 }