title: How to update browser cache from PHP?
body: <p>I have a PHP file <strong>get_css.php</strong> which generates CSS code more than 60 KB long. This code does not change very often. I want this code to be cached in user's browser.
  Now, when i visit a HTML page several times which includes <strong>get_css.php</strong> url to fetch css, my browser is loading all CSS contents from the server each time i visit the page.</p>
  
  <p>Browsers should get the contents from server only if the CSS code is changed on server side. If the css code is not changed, browser will use the css code from the browser cache.
  I cannot use any PHP function which is not allowed in Server Safe Mode.</p>
  
  <p>Is it possible? How can i achieve this?</p>