how to add a function to an html form code example

Example 1: html form

<form action="/action.php">
  <label for="fname">First name:</label><br>
  <input type="text" id="fname" value="Mike"><br><br>
  <label for="lname">Last name:</label><br>
  <input type="text" id="lname" value="Walker"><br><br>
  <input type="submit" value="Submit">
</form>

Example 2: posting with forms html

<form method="POST" action="INSERT WHERE YOU'RE SENDING THE DATA TO HERE">
	<input type="text" name="INSERT DATA KEY NAME HERE"> <!-- You don't have to have this line --> 
</form>