php＆operator构造[复制]

Question

This question already has an answer here:

• PHP “&” operator 7 answers
• Reference — What does this symbol mean in PHP? 18 answers

I got this piece of code which I'm analysing and it have this condition

if(($hint&self::HINT_WRITE  && $hint&self::HINT_NOWRITE) || ($hint&self::HINT_READ  && $hint&self::HINT_NOREAD))
{
    some code ..
}

Any Idea what '&' in '$variable&self::CONSTANT' means?

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