PHP Add if statement html variable [duplicate]

This question already has an answer here:

• What is the difference between client-side and server-side programming? 4 answers

I am trying to add if statemenet into $html variable. But it see php as a html tag. how can add this statement. Thanks

$html = '

    <?php if (x=y):?>

    <div>
          Help me )
    </div>

    <?php endif ?> 
';