How to call PHP function on the click of a Button

 <?php

      

        if(isset($_POST['button1'])) {

            echo "This is Button1 that is selected";

        }

        if(isset($_POST['button2'])) {

            echo "This is Button2 that is selected";

        }

    ?>

      

    <form method="post">

        <input type="submit" name="button1"

                value="Button1"/>

          

        <input type="submit" name="button2"

                value="Button2"/>

    </form>