How do file locking mechanisms in PHP, using the flock function, help prevent data corruption when multiple processes might write to the same file concurrently?

The flock function lets you acquire an exclusive or shared lock on a file before reading from or writing to it, preventing race conditions where multiple processes or requests attempting to write to the same file simultaneously could corrupt its contents or produce inconsistent results, which is especially important for applications that use file based storage for things like counters or logs that might be accessed concurrently by multiple simultaneous requests.

$handle = fopen('counter.txt', 'c+');
if (flock($handle, LOCK_EX)) {
    $count = (int) fread($handle, 1024);
    ftruncate($handle, 0);
    rewind($handle);
    fwrite($handle, $count + 1);
    flock($handle, LOCK_UN);
}
fclose($handle);