php gzinflate和base64_decode加密解密

<?php 
function encode_file_contents($filename) { 
$type=strtolower(substr(strrchr($filename,’.'),1)); 
if(’php’==$type && is_file($filename) && is_writable($filename)){// 如果是PHP文件 并且可写 则进行压缩编码 
$contents = file_get_contents($filename);// 判断文件是否已经被编码处理 
$pos = strpos($contents,’powered by arzn QQ:1314778′); 
if(false === $pos || $pos>100){ // 去除PHP文件注释和空白，减少文件大小 
$contents = php_strip_whitespace($filename); 
// 去除PHP头部和尾部标识 
$headerPos = strpos($contents,’<?php’); 
$footerPos = strrpos($contents,’?>’); 
$contents = substr($contents,$headerPos+5,$footerPos-$headerPos); 
$encode = base64_encode(gzdeflate($contents));// 开始编码 
$encode = ‘<?php’."\\n eval(gzinflate(base64_decode("."’".$encode."’".")));\\n\\n?>"; 
return file_put_contents($filename,$encode); 
} 
} 
return false; 
} 
//调用函数 
$filename=’code.php’; 
encode_file_contents($filename); 
echo "OK,加密完成！"
?>
//该片段来自于http://outofmemory.cn