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php版本比较函数version_compare()

来源: www.dedecms8.com 编辑:织梦吧 时间:2012-03-11点击:

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:

If you specify the third optional operator argument, you can test for a particular relationship. The possible operators are: <, lt, <=, le, >, gt, >=, ge, ==, =, eq, !=, <>, ne respectively.

This parameter is case-sensitive, so values should be lowercase.

    返回值:
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

标签: php版本比较

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