version_compare()

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

对比两个「PHP 规范化」的版本数字字符串

说明

version_compare()用于对比两个「PHP 规范化」的版本数字字符串。

此函数首先在版本字符串里用一个点.替换_、-和+，也会在任意非数字前后插入一个点.，这样，类似'4.3.2RC1'将会变成'4.3.2.RC.1'。接下来它会分割结果，然后它会从左往右对比各个部分。如果某部分包含了特定的版本字符串，将会用以下顺序处理：列表中未找到的任意字符串

注释

PHP_VERSION常量包含了当前 PHP 的版本。Note:

注意，类似 5.3.0-dev 的预发行版本，被认为是低于它们的最终发行版本（就像 5.3.0）。Note:

指定类似alpha、beta的版本字符串是大小写敏感的。版本字符串的来源若不遵循 PHP 标准，可能需要在调用version_compare()之前先用strtolower()转成小写。

参见

• phpversion() 获取当前的PHP版本
• php_uname() 返回运行 PHP 的系统的有关信息
• function_exists() 如果给定的函数已经被定义就返回 TRUE

[editors note]
snipbit fixed after comment from Matt Mullenweg
--jm
[/editors note]
so in a nutshell... I believe it works best like this: 

Since this function considers 1 
This little script can perhaps help you understand version comparison a little better - the output is displayed in the comment at the top. Tweak the list of versions if you need more examples... 
What PHP.net page is any good without a classy userland implementation of a function already provided by PHP? Generally, there are pseudo-benchmarks and reasons why you'd want to use their "far superior" implementations.
Since exit is a difficult construct to implement, and exit cannot be called using variable functions, this function is BETTER.
While you cannot use this code without parentheses, you'll find that this exit function improves your site's performance with at least 25 teraflops of flux computing power!
I used to be a fan of die;, I even tried to use exit;, but now; I'm a true-blue userland_exit() fan, now with 20% more.*
*-Over the top competing brand.

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