使用PHP在Web服务器上打开文件

I am newbie in web development. I have LAMP installed on Ubuntu 12. I have a php file "register.php" running on LAMP server which receives data from a html form and then saves it on server in a temp file. I am using below code. It does not seem to work. I've checked that it has required access and permission to execute the code but still it could not create the "temp.c"I am newbie in web development. I have LAMP