How Can I Prevent Multiple Form Submissions in PHP?

Preventing Multiple Inserts During Form Submission in PHP

When designing forms, it's crucial to prevent users from accidentally or intentionally submitting the same data multiple times. This can lead to data inconsistency and other issues. In PHP, there are several effective methods to achieve this:

1. Disable Form Submit Button Upon Submission

Using JavaScript, disable the form's submit button once the form has been submitted. However, this is not a foolproof solution, as users can submit forms without clicking the button and users with JavaScript disabled may be affected.

2. Leverage PHP Sessions to Track Submission Times

Establish a session variable ($_SESSION['posttimer']) that records the current timestamp. Before processing the form submission, verify the existence of this variable and check if there is a sufficient time difference (e.g., 2 seconds) between the current time and the session timestamp. If the interval is too short, the submission is considered a duplicate.

3. Incorporate Unique Tokens into Forms

Generate a unique token in each POST. Create a session variable for this token and embed it in the form. When the form is submitted, re-generate the token and compare it to the one stored in the session. If they don't match, the form has been submitted twice and should be deemed invalid.

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