Learning PHP and building a basic calculator, I get a Warning: Undefined array key when trying to retrieve values from HTML

Question

This is the code in question ~ Why will num1 and num2 not get added in between the php tags. It is a youtube tutorial so no community to ask there

<form action="site.php" method="get">
    
    <input type="number" name="num1">
    <br>
    <input type="number" name="num2">
    <br>
    <input type="submit">
</form>
<br>

<?php     
    
echo $_GET["num1"] + $_GET["num2"] ?>

Does this answer your question? [Reference - What does this error mean in PHP?](https://stackoverflow.com/questions/12769982/reference-what-does-this-error-mean-in-php) — pavel, Dec 06 '20 at 08:58

score 1 · Answer 1 · answered Dec 06 '20 at 09:01

1

In site.php...

<?php

if(isset($_GET['submit'])){

     echo $_GET["num1"] + $_GET["num2"];

}

?>


<form action="site.php" method="get">
    
    <input type="number" name="num1">
    <br>
    <input type="number" name="num2">
    <br>
    <input type="submit" name="submit" value="submit" />
</form>
<br>

PS: In a real world scenario, echo $_GET without any sanitization will expose you to security issues, but for tutorial purposes this answer should do the trick.

answered Dec 06 '20 at 09:01

Oliver M Grech

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Thank you! ~ does it make a difference if the php block is above or below the HTML? – Cristian Burloiu Dec 06 '20 at 09:08
In this case I prefer it because when teh answer is given, then you will see the form again (and you'll be able to make another calculation. Enjoy your PHP journey :) – Oliver M Grech Dec 06 '20 at 10:44

Learning PHP and building a basic calculator, I get a Warning: Undefined array key when trying to retrieve values from HTML

1 Answers1