Basic com between Resperry Pie and Arduino in PHP

gistfile1.aw

<?php
//(c) Lucas Lombard
        $error = "No Sockets";
        $list = shell_exec("screen -ls");
        if (strpos($list, $error) !== FALSE) {
                exec('screen -dmS arduino /dev/ttyAMA0 115200');
                sleep(1);
                exec('screen -p 0 -S arduino -X eval \'stuff \"2\"\'');
                header('Location: '.$_SERVER['PHP_SELF']);
    }
        elseif ($_GET['pin']) {
                $allowed = array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l");
                if (in_array($_GET['pin'], $allowed)) {
                        exec('screen -p 0 -S arduino -X eval \'stuff \"'.$_GET['pin'].'\"\'');
                        header('Location: '.$_SERVER['PHP_SELF']);
                }
                else {
                        echo "Caractere non pris en charge.<br />";
                }
        }
        else {
        exec('screen -p 0 -S arduino -X eval \'stuff \"1\"\'');
        exec('screen -p 0 -S arduino -X hardcopy /var/www/status.txt');
        $serial = exec('tail -1 /var/www/status.txt');
        $status = explode(";", $serial);
       
        $on="ON";
        $off="OFF";
        $checked_pin = 0;
        foreach ($status as $actual_pin) {
                if($actual_pin == 1){$text[$checked_pin]=$off;}else{$text[$checked_pin]=$on;}
                $checked_pin++;
        }
        $pin = 2;
        $checked_pin = 0;
        $pins_order = array("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l");
		$device = array("PIN 02", "PIN 03", "PIN 04", "PIN 05", "PIN 06", "PIN 07", "PIN 08", "PIN 09", "PIN 10", "PIN 11", "PIN 12", "PIN 13");
        foreach ($text as $actual_pin) {
                echo $device[$checked_pin].": ".$status[$checked_pin]." <a href=\"?pin=".$pins_order[$checked_pin]."\">". $actual_pin ."</a><br />";
                $checked_pin++;
                $pin++;
        }
        }