Click event on two buttons for if else condition is not working

Advance thanks for your help. I am not understanding why it is not working. I am a beginner and hence I am not finding the problem. Please anyone help me...

echo "<form method='POST'><br>
    <p>Would you Like to create your Account with Details Information<b>?
</b>
                <br><br> 
                <input type='button' id='yes' name='yes' value='Yes'/> 
                &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  
                <input type='button' id='no' name='no' value='No'/></p>
</form>";
        if ($_SERVER['REQUEST_METHOD'] === 'POST') {
        if (isset($_POST['yes'])) {
          echo "Yes Clicked";
         } else if (isset($_POST['no'])) {
         echo "<br><br><p> You have successfully Registered!!!</p>";
             }
        }