What is & in return($var & 1) in PHP

Question

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Reference - What does this symbol mean in PHP?

When I was reading this php page, I was not sure what & is doing in $var & 1.

function odd($var)
{
    // returns whether the input integer is odd
    return($var & 1);
}

Is it returning a reference? I am not sure.

If you can explain it or direct me a php page, I will appreciate it.

Thanks in advance.

PHP documentation: http://php.net/manual/en/language.operators.bitwise.php — Nick Stemerdink, Nov 13 '12 at 09:36

score 29 · Accepted Answer · answered Nov 13 '12 at 09:38

29

It's a bitwise-AND operation. All odd numbers have LSB (least significant bit set to 1), even numbers - 0.

So it simply "ANDs" two numbers together. For example, 5. It is represented as 101 in binary. 101 & 001 = 001 => true, so it is odd.

answered Nov 13 '12 at 09:38

Dmitri

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but 0 didn't return even numbers?,how can a function return same elements present in array – code-droid Dec 09 '20 at 04:52

score 9 · Answer 2 · edited Jun 20 '20 at 09:12

It is performing bitwise ANDing. That is a bitwise operator

$a & $b Bits that are set in both $a and $b are set.

In this case, return($var & 1); will do a bitwise AND against 0000....0001 returning 1 or 0 depending on the last bit of $var.

If the binary representation of a number ends in 0, it is even (in decimal).

If the binary representation of a number ends in 1, it is odd (in decimal).

score 4 · Answer 3 · answered Nov 13 '12 at 09:36

4

& is the bitwise and operator. In this case it will return 1 if $var is odd, 0 if $var is even.

answered Nov 13 '12 at 09:36

Joakim Nohlgård

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What is & in return($var & 1) in PHP

3 Answers3