What do the '&=' and '=&' operators do?

Question

Finding the answer to this is turning out to be much more difficult than I would have thought. Since I don\'t have a clue what you\'d call this, it\'s hard to run a Google s

Answer 1

=& assigns by reference

$a = 1;
$b =& $a;
$a++;
echo $b; // 2

From PHP Manual on References:

References in PHP are a means to access the same variable content by different names.

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&= is a bitwise AND assignment

$a = 1;
$a &= 1; // is the same as
$a = $a & 1;
echo $a; // 1

From Wikipedia on Bitwise AND:

A bitwise AND takes two binary representations of equal length and performs the logical AND operation on each pair of corresponding bits. In each pair, the result is 1 if the first bit is 1 AND the second bit is 1. Otherwise, the result is 0. For example:

    0101
AND 0011
  = 0001

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EDIT: For a practical example on bitwise operations, see my answer to Bitwise Operations in PHP