31      * @param callable $callback A PHP callable
35     public static function filterReferences($content, $callback)  argument
37         $content = static::filterUrls($content, $callback);
38         $content = static::filterImports($content, $callback, false);
39         $content = static::filterIEFilters($content, $callback);
48      * @param callable $callback A PHP callable
52     public static function filterUrls($content, $callback)  argument
56         return static::filterCommentless($content, function ($part) use (& $callback, $pattern) {
57             return preg_replace_callback($pattern, $callback, $part);
65      * @param callable $callback   A PHP callable
70     public static function filterImports($content, $callback, $includeUrl = true)  argument
74         return static::filterCommentless($content, function ($part) use (& $callback, $pattern) {
75             return preg_replace_callback($pattern, $callback, $part);
83      * @param callable $callback A PHP callable
87     public static function filterIEFilters($content, $callback)  argument
91         return static::filterCommentless($content, function ($part) use (& $callback, $pattern) {
92             return preg_replace_callback($pattern, $callback, $part);
100      * @param callable $callback A PHP callable
104     public static function filterCommentless($content, $callback)  argument
109                 $part = call_user_func($callback, $part);