PHP navbar using if condition & form to view content

<div class="navigation-bar" style="margin:1em 30%;">
<form action="" method="POST" style="display:inline;">
    <input type="submit" value="Hello World" name="about" class="btn">
    </form>
<form action="" method="POST" style="display:inline;">
    <input type="submit" value="How Are You" name="how" class="btn">
    </form>
<form action="" method="POST" style="display:inline;">
<button type="submit" value="How Are You" name="home" class="btn"> Home </button>
</form>
</div>
<br>
    <?php
       if (isset($_POST["about"]))
      {
        echo "Hello World";
    };
        if (isset($_POST["how"]))
        {
        echo "hello world How are you today";
    };
    if (isset($_POST["home"])) {
    include "ifelse.php";
    }
    ?>