What is & in return($var & 1) in PHP [duplicate]

Question

Possible Duplicate:
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.

Answer 1

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.

Answer 2

It is performing bitwise ANDing. That is a bitwise operator

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

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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).