Difference between & and && in PHP

Question

I am confused with & and &&. I have two PHP books. One says that they are same, but the another says they are different. I thought they

Answer 1

&& is & performed on operands reduced to either 1 or 0.

(In other words, && is a bitwise operator under the caveat that it changes its operands. That is, logical operations are a subset of bitwise operations.)