How can I detect a duplicate post in PHP? [duplicate]

This question already has an answer here: How to prevent duplicating DB insertions when refreshing? (1 answer) Closed 10 months ago.

I have a form which inserts the text (of an article) into a database. When a user submits an article (that has already been submitted) it gets submitted also into the db.

How can I detect a duplicate post (like on stackoverflow)?

Should I select everything from the database and check if the submitted post is like a one before. (I want to post the 开发者_Python百科duplicate alert on the article page as the first comment)

Any help appreciated.

Thanks...

---

Create an unique ID, e.g. with uniq_id(), put it in a hidden field within your HTML form, then save it in the database in a field that is set to UNIQUE. When the INSERT operation fails, you know that the POST has already been sent before.

---

If You will have hidden id, that you get from db when try to edit some content, You can use code like this:

if (isset($_POST['id']) && trim($_POST['id']) != '') {
    $query = 'UPDATE table_name
                    SET
                      `key` = \'' .$_POST['key']  . '\'
                    WHERE `id` = \'' . $_POST['id'] . '\'', 0;
  } else {
    $query = 'INSERT INTO table_name
                                  SET
                                `key` = \'' . $_POST['key'] . '\'', 0;
  }