Problem with the basel url in php directory

I have a problem

i have a index.php in that index
i link a

includes/meta.php

file. in that file i have style .css files and jquery .js files.

i have also

index.php

and a about/index.php

when i link the css from the include/meta.php to index.php the link works,

    <link href="vendor/css/style-front.css" type="text/css" rel="stylesheet" />

but does not work in this about/index.php directory

Why?

Someone here for a solution to fix this ?

i have tried this 

<link href="http://localhost:8888/vendor/css/style-front.css" type="text/css" rel="stylesheet" />

this works with the localhost:8888


but how fix this with like 



  <?php 
    print "<link href='{$base_url}vendor/css/style-front.css'/>";?>


Anyone here ?