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优先级问题

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Jun 20, 2016 am 09:37 AM

早上的时候碰见这个问题，
上边那个自增能理解，就是先自增，然后赋值，最后为4+4+1，下边那个结果为8是怎么理解的呢？自增的优先级应该比加号大吧

回复讨论(解决方案)

对于 echo 1 + $i + ++$i;
由于第二个运算符和第一个运算符是平级的
所以 1 + $i 被率先完成，之后的 ++$i 对 $i 的改变就影响不到前面了

而对于 echo $i + ++$i + 1
的确是因为 ++ 的优先级高于 +，从而使 ++$i 对 $i 的改变影响到了前面的 $i
但需要注意 ++$i 和 $i++ 的区别

+号的优先级比++高，建议去看一下优先级方面的资料，多练习就好

额，我把优先级的图片都贴在那了，怎么还是＋比＋＋
优先呢

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