Problem in my form submit flow, form data is too big

Here is my flow:

Form A post data to input.php as B

If data is invalid, B send data and error code into cookie and redirect to referer url (now is Form A)

Form A read data, error code in cookie, restate the form and display error message. The last thing is delete the cookie.

My problem is: How I still keep this 开发者_运维知识库flow if form data too heavy, because cookie size is limited.

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You can't. A cookie is limited to 4Kb. The only option you have is to store the data in a cache, or database (with an ID), and send that ID to back in the cookie.

When you redirect to your Form A, you can then re-read the data from the cache or database with the ID from the cookie.

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you could also have the form submit to the same page. Then you eliminate the problem of redirecting between pages and struggling to persist the data.