问题
I\'ve always assumed that - in the absence of constructor parameters - the parentheses (curly brackets) follow the class name when creating a class instance, were optional, and that you could include or exclude them at your own personal whim.
That these two statements were equal:
$foo = new bar;
$foo = new bar();
Am I right? Or is there some significance to the brackets that I am unaware of?
I know this sounds like a RTM question, but I\'ve been searching for a while (including the entire PHP OOP section) and I can\'t seem to find a straight answer.
回答1:
They are equivalent. If you are not coding by any code convention, use which you like better. Personally, I like to leave it out, as it is really just clutter to me.
回答2:
$foo = new bar() would be useful over $foo = new bar if you were passing arguments to the constructor. For example:
class bar {
public $user_id;
function __construct( $user_id ) {
$this->user_id = $user_id
}
}
-
$foo = new bar( $user_id );
Aside from that, and as already mentioned in the accepted answer, there is no difference.
来源：https://stackoverflow.com/questions/1945989/php-class-instantiation-to-use-or-not-to-use-the-parentheses