How to add two input values and display them in another input and fill the number in the input in the database?

How to add two input values and display them in another input and fill the number in the input in the database? There are four INPUT (A, B, C, D) in the form. two input values (A, B) and one input value (C) the size of one input value (B) is read from the database, and the other input (D) stores the result. how can we add two input values (A + C) is displayed in another input (D )? PS: how to fill the number read from the database in input (C)? thank you.

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Learn how to use Ajax.

Learn how to use Ajax.

I want to use it tomorrow. how can I fill the value of the read database into the input?

How can I fill in the number of reads from the database in the input field using PHP.
Adding two input values can be done in JS.
You have to post the relevant code.

Asynchronously load input fill to read the database

It can be implemented using js or ajax.

How can I fill in the number of reads from the database in the input field using PHP.
Adding two input values can be done in JS.
You have to post the relevant code.

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