I'm confuse. echo is use when you want to show that to front. but I guess importing css file url is not need for show to front because you just refer to location of url.
Sometimes, import css without echo, it's work fine.
<link rel="stylesheet" type="text/css" href="<?php base_url();?>css/animate.css"> but sometimes If I did not use echo, it will not work.
<link rel="stylesheet" type="text/css" href="<?php echo base_url();?>css/style.css"> What's this meaning?