What's the difference between include('file.php') and include 'file.php'

Question

Both include('file.php') and include 'file.php' work and seem to be interchangeable.

Does anyone know if there is any difference between the two syntaxes? Performance? Introduced in a particular version?

I know if you're going to write include $_SERVER['DOCUMENT_ROOT'] . '/file.php'; it would probably look clearer to write include($_SERVER['DOCUMENT_ROOT'] . '/file.php');

Answer 1

There is no difference. These are 'language constructs'. Syntactically this means that they can be used with or without braces. An example is echo statement.

echo("hello"); and echo "hello"; are the same

Answer 2

There's no difference, because include is a language construct that doesn't require parentheses, just like echo.

See also: include - scroll up a little bit