ARDUINO +PHP問題

<?php
$i = $_GET["action"];
$fp = fopen("com2", "w");// 我係用COM2
//echo chr($i);
fwrite($fp, chr($i));// 轉ASCII
fclose($fp);// 關閉 fp
?>

咁
ARDUINO個USBNUMBER呢

if (Serial.available() > 0) {
usbnumber = Serial.read();

我發覺唔係之前GET果個
E.G.
PHP 49->ARDUINO 唔係49,又唔係1
我試過 if(usbnumber==1)著LED同49著LED都唔得

唔知有無人明我講咩呢
另外我見有人連PHP要用php_serial.class.php
咁係咪好DD

THANKS