Use PHP functions or constants to quickly obtain the PHP version number and maximum file name length

In the previous article "PHP uses 3 predefined variables to quickly obtain form data", we learned about 3 magical predefined variables, and we can use them to quickly obtain the data submitted by the form. In fact, PHP not only has predefined variables, but also predefined constants. Using these predefined constants, we can quickly obtain some information about PHP, such as PHP version information, PHP extension directory, the type of operating system running PHP, etc. . This time I will show you some predefined constants.

The main content of today’s article is to talk about how to use PHP to quickly obtain the PHP version number and the maximum file name length supported by the current PHP version. Here are some methods to introduce to you.

1. Quickly obtain the PHP version number

1. Use the phpinfo() function to obtain the PHP version No.

When it comes to getting the PHP version number, the first thing that comes to mind is to use the phpinfo() function, which can return information about PHP configuration.

The output information includes: PHP version, server information and environment variables, PHP environment variables, operating system version information, path and environment variable configuration, HTTP headers, and copyright declaration, etc.

We only need to directly output the phpinfo() function:

<?php
echo phpinfo();
?>

Output result:

2. Use phpversion()Function to get the PHP version number

The phpinfo() function returns too much content. If you just want to get the PHP version number, just use the phpversion() function directly.

<?php
header("content-type:text/html;charset=utf-8");
echo "当前PHP的版本为：".phpversion();
?>

Output result:

3. Use predefined constantsPHP_VERSION

The PHP_VERSION constant can return the current PHP version number in the form of a string. The specific format is "major version number.sub version number.stage version number[extended information]".

<?php
header("content-type:text/html;charset=utf-8");
echo "当前PHP的版本为：".PHP_VERSION;
?>

Output result:

当前PHP的版本为：5.5.12

It can be seen that the output result of the predefined constant PHP_VERSION is the same as the phpversion() function.

In addition to the PHP_VERSION constant that can return PHP version information, the predefined constants PHP_MAJOR_VERSION, PHP_MINOR_VERSION, PHP_RELEASE_VERSION, PHP_VERSION_ID, and PHP_EXTRA_VERSION can also return part of the PHP version information.

PHP_MAJOR_VERSION (int)
当前 PHP 版本的主版本号，为整数形式（例如："5.2.7-extra" 版本是 int(5) ）。

PHP_MINOR_VERSION (int)
当前 PHP 版本的子版本号，为整数形式（例如："5.2.7-extra" 版本是 int(2) ）。

PHP_RELEASE_VERSION (int)
当前 PHP 版本的阶段版本号，为整数形式（例如："5.2.7-extra" 版本是 int(7) ）。

PHP_VERSION_ID (int)
当前 PHP 版本的整数，用于版本比较（例如："5.2.7-extra" 版本是 int(50207) ）。

PHP_EXTRA_VERSION (string)
当前 PHP 版本的”扩展信息“信息，为字符串形式（例如："5.2.7-extra" 版本是 '-extra' ）。 通常由发行版供应商用来指示包的版本。

2. Get the maximum file name length supported by the current PHP version

If you want to get the maximum file name length supported by the current PHP version, you can use the preset Define constant PHP_MAXPATHLEN, which can return the maximum file name (including path) length

<?php
header("content-type:text/html;charset=utf-8");
echo "当前 PHP 版本支持的最大文件名长度为：".PHP_MAXPATHLEN;
?>

Output result:

PHP is predefined There are many constants with different functions. In addition to obtaining PHP version information and obtaining the maximum file name length supported by the current PHP version mentioned above, you can also obtain the maximum/small integer supported by the current PHP, the smallest representable positive number, etc. Wait:

PHP_EOL (string)
当前平台中对于换行符的定义。

PHP_INT_MAX (int)
当前 PHP 版本支持的最大整型数字。在 32 位系统中通常为 int(2147483647)，64 位系统中为 int(9223372036854775807)。

PHP_INT_MIN (int)
当前 PHP 版本支持的最大整型数字。在 32 位系统中通常为 int(-2147483648)，64 系统中为 int(-9223372036854775808)。通常情况下 PHP_INT_MIN === ~PHP_INT_MAX。

PHP_INT_SIZE (int)
当前 PHP 版本的整数大小（以字节为单位）。

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