wordpress的样式表转换不能使用php标签

Im learning wordpress and I am using this youtube tutorial as reference https://www.youtube.com/watch?v=fZCFRQAcqLU

Im trying to convert my php code from

<link href="style.css" rel="stylesheet">

to

<link <?php bloginfo('stylesheet_url'); ?>rel="stylesheet">

After conversion, the page returns a blank page. I noticed that I cant use any php tags for this and I dont know why. it is already in my C:\xampp\htdocs\wordpress\wp-content\themes\wpbootstrap_master\index.php file. Any my Xamp is running fine. Help please

<link href="<?php echo bloginfo('stylesheet_url'); ?>" rel="stylesheet">

Use php code in href tag l

ie. href="<?php echo bloginfo('stylesheet_url'); ?>"

So I solved the question, turns out that the code is fine and it has no error. But since this is word press I needed to run it to its own server.