Using & as a comparison operator??

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New php-forum User
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Sun Mar 10, 2013 3:20 pm

I came across this code that kind of confused me:

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if ($strength & 1)
I've never heard of using & as a comparison operator. I've looked up comparison operators in the PHP manual and it doesn't list it as one. But apparently this code runs perfectly well. What is it doing? What's the purpose of using & as a comparison operator?

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Mon Mar 11, 2013 7:56 am

That is one of the bitwise operators supported by php, documented at

The ampersand is a bitwise AND. basically it looks at the binary representations of the operands, and returns true if one is contained in the other. In the example you've given, I'm assuming $strength is either a boolean value that is currently set to true, or it's an odd number. here's a drawn out example assuming the latter.

if $strength contained the number 33...
$strength's binary representation would be 100001 a bitwise and of that and 1 (000001) shows that they both have 1 in the 2^0 spot.

There are more examples in the manual, and I found an old example I gave someone on another forum forever ago on bitwise 'or' operations. ... l__bitwise

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Tue Oct 27, 2015 7:01 am

It is acting as bitwise operator in your code. It is used to check bit wise equivalency.

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