How to do i use php to collect data in html?

Question

i have learned html long ago with this app i learned php basic o want to use php to collect data from <form>

Answer 1

Based on form method:

<form action="" method="GET">
<input type=text name=data>
</form>

<?php
if(isset($_GET["data"])){
echo "<script>alert(' ".$_GET["data"]." ')</script>"} elseif (isset($_POST["data"])){/*code*/}
?>