PHP中的++ $ i和$ i ++有什么区别? [英] What's the difference between ++$i and $i++ in PHP?
问题描述
PHP中的++$i
和$i++
有什么区别?
What's the difference between ++$i
and $i++
in PHP?
推荐答案
++$i
是预递增的,而$i++
是后递增的.
++$i
is pre-increment whilst $i++
post-increment.
- 预递增:先递增变量
i
,然后取消引用. - 后递增:取消引用,然后递增
i
- pre-increment: increment variable
i
first and then de-reference. - post-increment: de-reference and then increment
i
利用PHP事实 允许您后递增($ i ++) 和预增量(++ $ i).含义 只要你不一样就一样 写类似$ j = $ i ++的东西, 但是预增量几乎是10% 更快,这意味着您应该 从后增量切换到预增量 有机会的时候 特别是在严密的循环中 特别是如果您对 微观优化!" - TuxRadar
"Take advantage of the fact that PHP allows you to post-increment ($i++) and pre-increment (++$i). The meaning is the same as long as you are not writing anything like $j = $i++, however pre-incrementing is almost 10% faster, which means that you should switch from post- to pre-incrementing when you have the opportunity, especially in tight loops and especially if you're pedantic about micro-optimisations!" - TuxRadar
为进一步澄清,PHP中的后增量已被记录为存储一个临时变量,该临时变量归因于这10%的开销(相对于前增量).
For further clarification, post-incrementation in PHP has been documented as storing a temporary variable which attributes to this 10% overhead vs. pre-incrementation.
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