Wordpress自定义css在头部

I'm trying to add page specific css in the head. For some reason the page completely goes white when I use the code below:

<?php if (is_page(5)) {
        <style>
        </style>
    } ?>

<style> is not right PHP syntax. Try this:

<?php if (is_page(5)) { ?>
    <style>
    </style>
<?php  } ?>