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'; 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

Answer 3

include（'file.php'）：首先计算（'file.php'）的值，原因是值为file.php，然后将file.php包含到当前文件中; include'file.php'：include file .php直接进入当前文件。如您所见，结果是一样的， 但第二种方式更有效。