&之间的差异和&&在PHP中 [英] Difference between & and && in PHP

问题描述

我对&和&&感到困惑.我有两本PHP书.一个说它们是相同的，但是另一个说它们是不同的.我以为他们也一样.

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 are same as well.

不是吗?

推荐答案

&是按位AND.请参见按位运算符.假设您执行14 & 7:

& is bitwise AND. See Bitwise Operators. Assuming you do 14 & 7:

    14 = 1110
     7 = 0111
    ---------
14 & 7 = 0110 = 6

&&是逻辑AND.参见逻辑运算符.考虑一下真值表:

&& is logical AND. See Logical Operators. Consider this truth table:

 $a     $b     $a && $b
false  false    false
false  true     false
true   false    false
true   true     true

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