如何使用PHP填充输入字段

Question

I'm trying to write a simple calculator html page where I ask for two numbers in separate text boxes, have the user click a button and then the result gets stored into a third text box. I'm trying to using PHP to resolve this but can't seem to display it the way I want. the echo line works fine, but I don't want that;

From HTML

     <form action="Add.php" method="get">
        <input for='num1' type="text"  name="num1" />
        <input for='num2' type="text" name="num2" />

        <input type="submit" value="Add Them" />
        <input type="text" name="AnswerBx" id="SumTotalTxtBx"/>
    </form> 

Add.php

     <?php 
        $num1 = $_GET["num1"];
        $num2 = $_GET['num2'];
        $sum = $num1+$num2;
        //echo "$num1 + $num2 = $sum";

        document.getElementById("SumTotalTxtBx").value = $sum;
    ?>

Answer 1

You are mixing PHP and Javascript here, go back to the PHP manual at : http://php.net/manual and read out how php works and interacts with the user.

Javascript is basicaly run on the client side while PHP is run on the server. You REQUEST php something and it returns a new HTML page for you.

That being said, its a too broad topic to help you fix your error.

Good luck