Get file extension from a file path.
Path::X($path, $fail = false);
Example:
$test_1 = Path::X('foo\bar\baz.qux');
$test_2 = Path::X('foo\bar\baz', 'txt');
$test_3 = Path::X('foo\bar\baz.QUX');
Result:
$test_1 = 'qux';
$test_2 = 'txt';
$test_3 = 'qux';