PHP function to parse a blob of CSS and count up the total number of selectors present. Useful if you need/want to factor this into your test suite to make sure your CSS files never reach the 4095 limit in IE9 and lower.

countSelectors.php

<?php

/**
 * Parse out a given string containing CSS and count up the total number of
 * selectors that are present in it.
 *
 * @return integer
 */
function countSelectors($css) {
  $css = preg_replace('/\{(.*?)\}/s', '', $css);
  $css = preg_replace('/[,]/', "\n", $css);
  $selectors = explode("\n", $css);
  $selectors = array_filter($selectors);

  return count($selectors);
}