使用PHP文件扩展名编写动态CSS样式表效率较低吗？

Question

Ive been trying to think of ways to dynamically change a style based off of input from a website back-end (through a language like PHP). Normally I have my stylesheets be separate CSS-extension files, but these won't allow for PHP tags natively. It is, after all, extra markup in your HTML file than having all of your styles be in a separate file. Is the usage of the HTML <style> tag perhaps slower/less efficient than using a stylesheet?

Answer 1

The W3C Recommendation for CSS 2.1 contains a section on Conformance: Requirements and Recommendations, which makes no reference to filename extension but does state:

3.4 The text/css content type

CSS style sheets that exist in separate files are sent over the Internet as a sequence of bytes accompanied by encoding information. The structure of the transmission, termed a message entity, is defined by RFC 2045 and RFC 2616 (see [RFC2045] and [RFC2616]). A message entity with a content type of "text/css" represents an independent CSS document. The "text/css" content type has been registered by RFC 2318 ([RFC2318]).

Therefore, provided that the file is served with the text/css content type (and that any cacheing concerns are addressed as mentioned in @Fluffeh's answer), you should not have a problem. In PHP, the content type can be set with a call to header() before any output is sent:

<? header('Content-type: text/css'); ?>