How can PHP handle simultaneous entries in a guestbook to prevent data loss or conflicts?

To handle simultaneous entries in a guestbook and prevent data loss or conflicts, we can use a locking mechanism to ensure that only one entry is processed at a time. This can be achieved by using file locking or database transactions to prevent multiple users from writing to the guestbook simultaneously. 

$guestbookFile = 'guestbook.txt';

// Acquire an exclusive lock on the guestbook file
$handle = fopen($guestbookFile, 'a');
if (flock($handle, LOCK_EX)) {
    // Write the guestbook entry to the file
    fwrite($handle, "New guestbook entry\n");
    
    // Release the lock and close the file
    flock($handle, LOCK_UN);
    fclose($handle);
} else {
    echo "Unable to acquire lock on guestbook file";
}

Keywords

concurrency control database transactions locking mechanisms isolation levels optimistic concurrency control

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