PHP include vs include_once（速度）
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PHP include vs include_once (speed)
提问by Ricket
Possible Duplicate:
Why is require_once so bad to use?
I've read somewhere that the include_onceand require_oncestatements in PHP were slower than their non-once counterparts. Is this a significant slowdown? Has there been any testing or studies of this, and has it changed in recent versions of PHP?
我在某处读到PHP 中的include_onceandrequire_once语句比它们的 non-once 语句慢。这是一个显着的放缓吗？是否对此进行了任何测试或研究，并且在最新版本的 PHP 中是否发生了变化？
回答by SW4
The speed increase is minimal and comes as a reference check is conducted to prevent code duplication. The 'once' appendage is a preventative measure against the same code being executed/included twice..this performing this check comes at a minor speed cost.
速度增加很小，并且进行了参考检查以防止代码重复。'once' appendage 是针对同一代码被执行/包含两次的预防措施......执行此检查的速度成本很小。
If there is ever an instance where you are using _oncelook into why it is the case, is you code really built in the most efficient way? It is often better to remove the need to rely on _onceand produce better code (easier said than done!).
如果曾经有一个您正在使用的实例，请_once查看为什么会出现这种情况，您的代码是否真的以最有效的方式构建？消除对依赖的需求_once并生成更好的代码通常更好（说起来容易做起来难！）。
See:
看：
http://forums.digitalpoint.com/showthread.php?t=1693837
http://forums.digitalpoint.com/showthread.php?t=1693837
http://www.phpbb.com/community/viewtopic.php?f=71&t=565933
http://www.phpbb.com/community/viewtopic.php?f=71&t=565933
http://www.sitepoint.com/forums/showthread.php?t=269085
http://www.sitepoint.com/forums/showthread.php?t=269085
http://www.quora.com/What-is-the-difference-between-functions-include-and-include_once-in-PHP
http://www.quora.com/What-is-the-difference-between-functions-include-and-include_once-in-PHP
回答by Nicolas
The include_once and require_once functions are slower than include and require, simply because they keep track of the files that have already been included, to avoid including them more than once.
include_once 和 require_once 函数比 include 和 require 慢，因为它们跟踪已经包含的文件，以避免多次包含它们。
But that shouldn't matter AT ALL, since there are probably many ways to optimize your application, way more efficient than this one.
但这根本不重要，因为可能有很多方法可以优化您的应用程序，比这一种更有效。
