Avoiding race conditions when opening a file for writing

[johnmerlino1]

I have the following code:

$fp = fopen(“path_to_file”, ‘a’);
flock($fp, LOCK_EX);
fwrite($fp, $string);
flock($fp, LOCK_UN);  
fclose($fp);

If I try to lock the file in two different places at the same time, this will cause a race condition. How can I prevent this? I know in Java, for example, it has a concurrent library which contains reentrant lock, which basically tries to get the lock and if can't waits. What can I do in PHP?

[kicken]

flock will wait if it cannot acquire the lock. If you have two different scripts trying to get a lock on the file then one of them will succeed and the other will be blocked until the first releases the lock.