How to receive data from Form_A and send to Form_B ? - 26.07.19

If you use CI4 in your project then it has such methods as:
https://codeigniter4.github.io/userguide...direct#old
1) old(); - Provides a simple way to access “old input data” from submitting a form.
2) return redirect()->back()->withInput(); - Keep the old input values upon redirect so they can be used by the `old()` function.

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