在PHP中分配变量值时，“＆=”和“=＆”之间有什么区别？

Question

我知道=&通常意味着“通过引用分配”，但是如果我们反转这两个字符会发生什么，因为我在很多PHP脚本中看到了这一点？

Answer 1

$a &= $b是$a = $a & $b缩写，它是按位和运算符。

Answer 2

It's the compound bitwise AND /assignment operator:

$x = 0x01;
$y = 0x11;

$y &= $x; // bitwise AND $y and $x, assign result back to $y
var_dump($y == 0x01); // true

Answer 3

&= is a compound assignment operator , whereas =& is actually two separate operators ( = and & ), pushed together. This is legal syntax because PHP doesn't demand whitespace between them.

&= performs a bitwise AND operation between the left hand side and right hand side, then assigns the result to the left hand side variable.

$x = 1;
$x &= 0; // $x === 0 now. A more verbose syntax would be "$x = $x & 0;"

On the other hand =& should really be expanded to = & as the operators are seperate. This is known as assignment by reference . The = is your standard assignment operator, and the & when prefixed before a variable name returns the reference to the variable.

$y = "foobar";
$x = &$y; // $x now holds a reference to $y.