What's the difference between these 2 piece of codes?
<?php
$object1 = new User();
//^^
$object1->name = "Hello";
echo $object1->name;
class User {}
?>
And:
<?php
$object1 = new User;
//^
$object1->name = "Hello";
echo $object1->name;
class User {}
?>
I get the same output:
Hello
So is there any difference if I use the parentheses or not in:
$object1=new User;
The are exactly the same, you can compare opcode of these 2 scripts:
1 script:
$object1=new User();
$object1->name="Hello";
echo $object1->name;
class User {}
opcode:
line # * op fetch ext return operands
---------------------------------------------------------------------------------
3 0 > FETCH_CLASS 4 :0 'User'
1 NEW $1 :0
2 DO_FCALL_BY_NAME 0
3 ASSIGN !0, $1
4 4 ASSIGN_OBJ !0, 'name'
5 OP_DATA 'Hello'
5 6 FETCH_OBJ_R $5 !0, 'name'
7 ECHO $5
6 8 NOP
9 > RETURN 1
2 script:
$object1=new User;
$object1->name="Hello";
echo $object1->name;
class User {}
opcode:
line # * op fetch ext return operands
---------------------------------------------------------------------------------
3 0 > FETCH_CLASS 4 :0 'User'
1 NEW $1 :0
2 DO_FCALL_BY_NAME 0
3 ASSIGN !0, $1
4 4 ASSIGN_OBJ !0, 'name'
5 OP_DATA 'Hello'
5 6 FETCH_OBJ_R $5 !0, 'name'
7 ECHO $5
6 8 NOP
9 > RETURN 1
Rizwan Shah
Both are equal. if you not using any code convention then use which you like. I think $object1 = new User() would be useful over $object1 = new User. if you were passing arguments to the constructor.
来源：https://stackoverflow.com/questions/28914283/is-there-a-difference-between-instantiation-with-parentheses-or-without