php版本比较函数version_compare()_PHP_编程开发_程序员俱乐部

php中比较php版本，一般用version_compare()函数，帮助文档见：http://php.net/manual/en/function.version-compare.php
用途：Compares two "PHP-standardized" version number strings。
语法：version_compare ( string $version1 , string $version2 [, string $operator ] )
具体描述：version_compare() compares two "PHP-standardized" version number strings. This is useful if you would like to write programs working only on some versions of PHP.

The function first replaces _, - and + with a dot . in the version strings and also inserts dots . before and after any non number so that for example '4.3.2RC1' becomes '4.3.2.RC.1'. Then it splits the results like if you were using explode('.', $ver). Then it compares the parts starting from left to right. If a part contains special version strings these are handled in the following order: any string not found in this list < dev < alpha = a < beta = b < RC = rc < # < pl = p. This way not only versions with different levels like '4.1' and '4.1.2' can be compared but also any PHP specific version containing development state.

??? 其中第三个可选参数是比较符：

By default, version_compare() returns -1 if the first version is lower than the second, 0 if they are equal, and 1 if the second is lower.

?

When using the optional operator argument, the function will return TRUE if the relationship is the one specified by the operator, FALSE otherwise.

??? 从下面的例子，就可以很好地说明version_compare的用法：

<?php
if?(version_compare(PHP_VERSION,?'6.0.0')?>=?0)?{
????echo?'I?am?at?least?PHP?version?6.0.0,?my?version:?'?.?PHP_VERSION?.?"\n";
}

if?(version_compare(PHP_VERSION,?'5.3.0')?>=?0)?{
????echo?'I?am?at?least?PHP?version?5.3.0,?my?version:?'?.?PHP_VERSION?.?"\n";
}

if?(version_compare(PHP_VERSION,?'5.0.0',?'>='))?{
????echo?'I?am?using?PHP?5,?my?version:?'?.?PHP_VERSION?.?"\n";
}

if?(version_compare(PHP_VERSION,?'5.0.0',?'<'))?{
????echo?'I?am?using?PHP?4,?my?version:?'?.?PHP_VERSION?.?"\n";
}
?>

??? 最近在nagios的图表监控插件pnp安装中遇到一个错误提示：Kohana requires PHP 5.2 or newer.查看页面源码，发现如下语句：
version_compare(PHP_VERSION, '5.2', '<') and exit('Kohana requires PHP 5.2 or newer.');
也就是版本不满足就退出。

??? strcmp()的字符串比较函数，也可以进行比较，但像下面这样，就会出现错误：
4.1.10与4.1.2比较
strcmp(“4.1.10″, “4.1.2″); 会返回-1 错误
version_compare(“4.1.10″. “4.1.2″); 就会返回1 正确

转载自： http://ljhzzyx.blog.163.com/blog/static/3838031220106553216892/