How do I make a website field mandatory?

There is no way within standard HTML code to make a field mandatory because it does no evaluation. For this you need JavaScript or, more robustly, PHP.

First, it is a good idea in your HTML to say which fields are mandatory or not, for instance by marking them with a '*' by them.

Then you do the check in your PHP code after the form has been submitted. So let's say we have a field called 'mandatory' and the form was submitted by post, here is how we can check for a value:


<?php

$anyvalue = $_POST[mandatory];

if(!$anyvalue) { echo "No value - please go back and fill in"; }

//don't use if you want '0' to be a valid value



//a better test for the variable to have some contents



$length = strlen($anyvalue);

if(!$length) { echo "No value - please go back and fill in!"; }

?>

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