define(SAFEVALUE,25);
define(DANGEROUSVALUE,28);

yDisableExceptions(); // I like to handle errors myself :-)

1. if  (yRegisterHub("http://127.0.0.1:4444",$errmsg)<>YAPI_SUCCESS)
     Die("yRegisterHub failed : $errmsg");
     
   $LightRelay = yFirstRelay();
   $TempSensor = yFirstTemperature(); 
2. if (is_null($LightRelay)) die("Relay not found");
   if (is_null($TempSensor)) die("Temperature sensor not found");

$safeState = true;
$LightRelay->set_state(Y_STATE_A);

1. while (true)
    {   $temp = $TempSensor->get_currentValue();
        Printf("$temp °C\n");
        if (($temp>=DANGEROUSVALUE) && $safeState) 
          { $safeState =false;
            $LightRelay->set_state(Y_STATE_B);
            mail(This email address is being protected from spambots. You need JavaScript enabled to view it.'">'This email address is being protected from spambots. You need JavaScript enabled to view it.', 
                 'Server room overheat', 
                 "Warning:  temperature in server room$temp °C",
                 'From: This email address is being protected from spambots. You need JavaScript enabled to view it.'">This email address is being protected from spambots. You need JavaScript enabled to view it.' . "\r\n" );
          }
        if (($temp<=SAFEVALUE) && !$safeState)
          { $safeState =true;
            $LightRelay->set_state(Y_STATE_A);
          }
        ySleep(1000,$errmsg); 
    }