In file_is_text(): mime_content_type is deprecated and not necessarily available

Instead of the above regexp, we can use file_extension() Limoande function

    $ext = strtolower(file_extension($filename));
    if($mime = mime_type($ext)) return substr($mime,0,5) == "text/";

The mime_content_type() compatibility alternate function must be rewritten to apply above changes. And it should be renamed to avoid confusion and be used even if mime_content_type() native function exists.

So, replace:

if(!function_exists('mime_content_type')) {
  /**
   * Detect MIME Content-type for a file
   *
   * @param string $filename Path to the tested file.
   * @return string
   */
  function mime_content_type($filename)
  {
    $ext = strtolower(array_pop(explode('.', $filename)));
    if($mime = mime_type($ext)) return $mime;
    elseif (function_exists('finfo_open')) {
        $finfo = finfo_open(FILEINFO_MIME);
        $mime = finfo_file($finfo, $filename);
        finfo_close($finfo);
        return $mime;
    }
    else return 'application/octet-stream';
  }
}

with something like this:

  /**
   * Detect MIME Content-type for a file
   *
   * @param string $filename Path to the tested file.
   * @return string
   */
  function file_mime_content_type($filename)
  {
    $ext = file_extension($filename); /* strtolower isn't necessary */
    if($mime = mime_type($ext)) return $mime;
    elseif (function_exists('finfo_open')) {
        $finfo = finfo_open(FILEINFO_MIME);
        $mime = finfo_file($finfo, $filename);
        finfo_close($finfo);
        return $mime;
    }
    else return 'application/octet-stream';
  }

And use it in file_is_text():

function file_is_text($filename)
{
    if($mime = file_mime_content_type($filename)) return substr($mime,0,5) == "text/";
    return null;
}