PHP. Detects the file extension from a given string.

php_get_file_extension.md

#Get File Extension

Detects the file extension from a given string. This function returns the text following the last dot of the file name, so more complicated file extensions such as .tar.gz are only returned as ".gz".

function file_ext($file) {
  $last_dot = strrpos($file, '.');
  if ($last_dot !== false) {
    return strtolower(substr($file, $last_dot + 1));
  }
  return 'file';
}

Examples:

echo file_ext('test.txt'); // "txt"
echo file_ext('PAGE.HTML'); // "html"
echo file_ext('config'); // "file"