Arduino sending & receiving data to & from Beaglebone Black

/*
 * using PHPSerial (https://github.com/Xowap/PHP-Serial) on Beaglbone Black to send ON/OFF to Arduino's LED
 * and read LM35 sensor temperature. See Arduino code here: http://pastebin.com/J6fCNguP
 * almost all code is by: http://paolosarteschi.altervista.org/wp/?p=375
 * to connect Arduino & Beaglebone Black use:
 * www.instructables.com/id/How-to-make-a-BeagleBone-and-an-Arduino-communicat/?ALLSTEPS
 *
*/

int tempPin = 0;// pin cui è collegato il sensore
int temp;

int LED = 13;
int statoled;
char oldval='a',val = '0';
void setup() {
  pinMode(LED,OUTPUT);
  Serial.begin(9600);
}

void loop () {

  val = Serial.read();
  if(val!=oldval)
  oldval=val;

  if(oldval=='s'){
  digitalWrite(LED,LOW);
  Serial.print(0);
  }
  else if (oldval=='a'){
  digitalWrite(LED,HIGH);
  Serial.print(1);
  }
  else if (oldval=='r'){
  statoled = digitalRead(LED);
    if (statoled==0){
    Serial.print(0);
    }
    else {
    Serial.print(1);
    }
  }

temp  = ( 4.4 * analogRead(tempPin) * 100.0) / 1024.0;
Serial.print(temp);
delay(200);

}