PHPSerial on Beaglebone Black

<?
/*
 * using PHPSerial (https://github.com/Xowap/PHP-Serial) on Beaglebone 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
 *
*/

error_reporting(E_ALL);
ini_set("display_errors", 1);
define("PORT","/dev/ttyO2");
include "php_serial.class.php";

$serial = new phpSerial;
$serial->deviceSet(PORT);
$serial->confBaudRate(9600);
$serial->confParity("none");
$serial->confCharacterLength(8);
$serial->confStopBits(1);
$serial->confFlowControl("none");
$serial->deviceOpen();
$title = "";

global $temperatura, $statoled;

    $serial->sendMessage("r");
    sleep(0.2);
    $serialread = $serial->readPort();

    if($serialread==""){
    //echo "errore - valori assenti";
    header ('Location:' . $_SERVER['PHP_SELF']);
    }

    elseif(strlen($serialread)!=3){
    //echo "errore - valori non coerenti";
    header ('Location:' . $_SERVER['PHP_SELF']);
    }

    else{
    $statoled = substr($serialread,0,1);
    $temperatura = substr($serialread, 1,2);

        if ($statoled == 1){
        $title = "SPEGNI LED";
        //echo $title;
        }
        else {
        $title = "ACCENDI LED";
        //echo $title;
        }

    }

 if (isset($_GET['action'])) {

    if ($_GET['action'] == "on") {
        $serial->sendMessage("a");
        header ('Location:' . $_SERVER['PHP_SELF']);
        }
    else if ($_GET['action'] == "off") {
        $serial->sendMessage("s");
        header ('Location:' . $_SERVER['PHP_SELF']);
        }

    $read = $serial->readPort();

}
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <title>TEST LED - <?=$title?></title>
 </head>

 <body>
<?


if ($statoled == 1){

?>
<a href="<?=$_SERVER['PHP_SELF'] . "?action=off" ?>">
<button style="color: red;width:250px"><h1>SPEGNI LED</h1></button></a>
<?
}
else if ($statoled == 0){

?>
<a href="<?=$_SERVER['PHP_SELF'] . "?action=on" ?>">
<button style="color: green;width:250px"><h1>ACCENDI LED</h1></button></a>
<?
}

?>
<h2 style="font-family:arial;color: darkblue">
Temperatura:
<?
echo "$temperatura&deg; C";
?>
</h2>
 </body>
</html>