What are the commonly used predefined constant functions in php?

PHP provides many predefined constant functions: PHP_VERSION returns the PHP version. PHP_OS returns the current operating system name. PHP_SAPI returns the server API that PHP runs under. PHP_EOL returns the system newline character. E_ALL returns an integer containing all error levels.

Commonly used predefined constant functions in PHP

PHP provides a large number of predefined constant functions. Help us get information about the current PHP environment and scripts. The following are some of the commonly used functions:

1. PHP_VERSION

Returns the version number of PHP, such as "7.4.25" or "8.1.6".

2. PHP_OS

Returns the name of the current operating system, such as "Linux", "Windows" or "macOS".

3. PHP_SAPI

Returns the server API used by the current PHP run, such as "cli" (command line interface), "apache2handler" (Apache module) or " cgi-fcgi" (CGI/FastCGI).

4. PHP_EOL

Returns the string containing the newline character in the current system, such as "\n" (Unix) or "\r\n" (Windows).

5. E_ALL

Returns an integer containing all error levels, such as 2047.

6. E_ERROR

Returns an integer indicating the error level E_ERROR, for example 1.

7. E_WARNING

Returns an integer indicating the error level E_WARNING, for example 2.

8. E_NOTICE

Returns an integer indicating the error level E_NOTICE, for example 8.

9. E_USER_ERROR

Returns an integer indicating the error level E_USER_ERROR, for example 256.

10. E_USER_WARNING

Returns an integer indicating the error level E_USER_WARNING, for example 512.

11. E_USER_NOTICE

Returns an integer representing the error level E_USER_NOTICE, such as 1024.

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