How to initialise CSS statements from the function.php file (Wordpress)?

I have the following CSS conditional statement in my function.php file:

 function logo_exists() {
 global $options;
    ?><style type="text/css">
  #header h1 a {
  <?php
  if ( $options['logo'] == NULL ) { ?>
      float: left;
   text-indent: 0;
  <?php } else { ?>
   background: url(<?php echo $options['logo']; ?>) no-repeat scroll 0 0;
   float: left;
   text-indent: -9999px;
   width: 160px;
   height: 80px;
  }
  <?php } ?>
    </style><?php
}

example:

        (...same code as above...)

       width: 160px;
       height: 80px;
      }
      <?php } ?>
        <开发者_如何学编程/style><?php

        add_option('logo_exists');

}

I'm not sure how to "add" or "initialise" it.

I tried: add_option('logo_exists'); and add_action('logo_exists'); but it didn't work.

What's the Wordpress "add" command for conditional CSS statements in the function.php file?

---

Instead of using this variation, you could use wordpress conditions: is_home() is_singular() (for page/article) is_single() is_page() ad so on.

Besides that, WP automatically add an extra class to body element and you can relate to that to build your css selectors.