One of the attractions of PHP is that you can use it as much or as little as you need.

Have a static site that needs one page with dynamic content? Just make that one page PHP, and do whatever you need.

Need a basic caching/templating engine? Smarty.

Need a basic linear blog? Hack something with Wordpress.

Need a more complex site with categories and plugins, that fits into a wide community? Drupal.

Need to have full control over how the thing works? Use something like CodeIgniter or Cake.

Lots of options out there, and PHP is stupidly simple to deploy compared to most other technologies.