Protect a file of being overwritten for a short time

DSC_Garfield

There are 2 who can update pageX. When they login in, they get on their main page, there is a link to the form to update pageX. When somebody klicked that link, and is in the update field, a message should be displayed at the other person if he klicks the "update page" link, while the other is still busy (to protect the file for overwriting).

I had a way to do this:
When one of them klicks the link, a temporary file gets created.
When the other person klicks the link, it first checks if the temp file is there, if so --> "plz wait" message.
When the first person klicks the submit button to update his page, I delete the temp file right after the data has been written to the page he wanted to update.

The problem is: if the updating person closes his browser without running the script to delete the temporary file, it will be there forever.

I believe there are better ways to do this. Do you have any suggestions?

Xoid

well... the only way I can think of to protect a file for a short while would be to us;

flock()

// Shared
// Allows other processes to read file but stops writing

flock($fp,LOCK_SH)

// Exclusive
// Stops other processes from reading from or writing to a file

flock($fp,LOCK_EX)

// Release
// Releases the file from exclusive or shared locks
flock($fp,LOCK_UN)

Hope this helps!

DSC_Garfield

Thanks for the reply
Well, I tried flock, but I'm not sure if it is working on my server.

This is the way I use it:

$file = "file.txt";
$fp = fopen($file,"w");
flock($fp,2);
fputs($fp,$data);
flock($fp,3);
fclose($fp);

But the second person shouldn't be able to view the file, while the other person is still in the update field. Should I put flock($fp,2) on the update page then? And flock($fp,3) right after the data has been written to the file?