Switch Statement with user input - php

Question

as a heads up I'm new at coding.
I'm trying to make a switch statement that will give the user the number that they have inputted into its proper roman number (only numbers from 1-10).
<form action="#" method="post">
Type a number from 1-10. <input type="text" name="num"/>
<input type="submit" name="submit">
</form>
<?php
switch (isset($_POST['submit'])) {
//$num = (int)$_POST["num"];
case 1:
echo "I";
break;
case 2:
echo "II";
break;
case 3:
echo "III";
break;
case 4:
echo "IV";
break;
case 5:
echo "V";
break;
case 6:
echo "VI";
break;
case 7:
echo "VII";
break;
case 8:
echo "VIII";
break;
case 9:
echo "IX";
break;
case 10:
echo "X";
break;
}
?>
Currently, this is what I have but I don't know of a way to get the switch statement to use the number that was provided by the user. Any help?
Thanks in advance.

Answer 1

The input that the user will enter a number in it has a name attribute of 'num', so to get what the user has entered, you'll use $_POST['num'].
// if the form has been submitted
if(isset($_POST['submit'])) {
$num = (int) $_POST['num'];
switch($num) {
case 1:
echo "I";
break;
case 2:
echo "II";
break;
case 3:
echo "III";
break;
case 4:
echo "IV";
break;
case 5:
echo "V";
break;
case 6:
echo "VI";
break;
case 7:
echo "VII";
break;
case 8:
echo "VIII";
break;
case 9:
echo "IX";
break;
case 10:
echo "X";
break;
default:
echo 'wrong number or you probably entered a number less than 1 or higher than 10';
}
}

Answer 2

First you make sure you have a something
Notice I am using $_POST['num']
$num = $_POST['num'] ?? 0;
Now you check
switch($num){
case 1:
echo 'I';
break;
case 2:
echo 'II';
break;
...
...
I would do it a bit differently, and even that is not the most efficiet transformation.
echo (([1=>'I', 2=>'II',3=>'III',....,9=>'IX'])[$_POST['num']]) ?? '';

Answer 3

isset($_POST['submit']) returns a boolean, which is not the integer in the range 1-10 that your switch statement expects. You probably meant to use $_POST['num'].
An array is a more compact way to encapsulate your logic instead of a long and potentially error-prone switch statement. Each array index maps to a numeral as follows:
<form action="#" method="post">
Type a number from 1-10. <input type="text" name="num">
<input type="submit" name="submit">
</form>
<?php
$numerals = ['', 'I', 'II', 'III', 'IV', 'V', 'VI', 'VII', 'VIII', 'IX', 'X'];
if (isset($_POST['num'])) {
echo isset($numerals[$_POST['num']]) ? $numerals[$_POST['num']] : "error";
}
?>

Answer 4

You can use the following solution to solve your problem:
$input = $_POST['num'];
if($input){
switch($input) {
....
}
}