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Editorial Team
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Asked: 2026-06-14T01:05:31+00:00

First of all, I am not en expert at programming, so please explain things

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First of all, I am not en expert at programming, so please explain things a bit if you can so I can understand them better. I am trying to make a calculator that will have some fields the user can fill out, and will display the last output. Basically this:

Variable boxes
“Go” button
Results display here after Go is pressed.

And the user can change the boxes and click go again to refresh with the new results.

I do not want to use Java for this if at all possible. Please help me with an HTML/PHP solution.

I have this page nammed “isset.php”

<?php 
session_start(); 
error_reporting(E_ALL);
ini_set('display_errors', '1');?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
</head>
<body>

<?php
     if(isset($_POST['submit']))
        {
        $a = $_POST['a'];
        $b = $_POST['b']; 
        $sf = $a-(2*$b);
        echo "<br><br>Safety Factor is ";
        echo $sf;
        } 
     else {
        echo "Your results will display here after you use the calculator.";
          }
 ?>

 <br>Calculator
 <form name="submit" method="post" action="isset.php">
 <table width="450px">
     <td valign="center">
     <label for="a">a</label></td>
        <td valign="center">
        <input type="text" name="a" value="45"></td></tr>
     <td valign="center">
     <label for="b">b</label></td>
        <td valign="center">
        <input type="text" name="b" value="16"></td></tr>         
 <tr><td colspan="2" style="text-align:center">
 <input type="submit" value="Calculate!">
 </td></tr></table>
 </form>        

</body>
</html>
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1 Answer

  1. Editorial Team

    Change <input type="submit" value="Calculate!"> to <input name="submit" type="submit" value="Calculate!">

    The reason your code is not working is because you’re checking to see if the post data contains the key submit but you haven’t defined it within your form (you do this by adding a name attribute).

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