What are the built-in constants in php?

php's built-in constants include PHP_VERSION, PHP_OS, PHP_EOL, PHP_INT_MAX, PHP_INT_MIN, PHP_INT_SIZE, PHP_ROUND_HALF_UP, PHP_ROUND_HALF_EVEN, PHP_ROUND_HALF, PHP_FLOAT_MAX, PHP_FLOAT_DIG, PHP_BINARY, PHP_SAPI, PHP_SELF, etc.

The operating environment of this article: Windows 10 system, PHP8.1.3 version, Dell G3 computer.

PHP's built-in constants are some predefined constants that can be used directly in PHP scripts. There are many these constants. Here are some common built-in constants:

PHP_VERSION: The version number of the current PHP parser.

PHP_OS: The name of the operating system running the PHP parser.

PHP_EOL: The newline character of the current operating system.

PHP_INT_MAX: The maximum integer value that the current PHP parser can represent.

PHP_INT_MIN: The smallest integer value that the current PHP parser can represent.

PHP_INT_SIZE: The size (number of bytes) of the integer type that the current PHP parser can handle.

PHP_ROUND_HALF_UP: Constant for rounding 8. PHP_ROUND_HALF_DOWN: Constant for rounding.

PHP_ROUND_HALF_EVEN: Constant used for rounding.

PHP_ROUND_HALF: Constant used for rounding.

PHP_FLOAT_MAX: The maximum floating point value that the current PHP parser can represent.

PHP_FLOAT_MIN: The smallest floating point value that the current PHP parser can represent.

PHP_FLOAT_DIG: The number of significant digits of floating point numbers that the current PHP parser can represent.

PHP_BINARY: The binary path of the PHP parser.

PHP_SAPI`: The interface type of the current PHP parser (such as "cli" or "cgi-fcgi").

PHP_SELF: The file name of the currently executing script.

PHP_MAXPATHLEN: The maximum path length allowed for the current operation.

PHP_MAX_EXECUTION_TIME: The maximum execution time (seconds) allowed by the current PHP parser.

PHP_OUTPUT_HANDLER_START: The start identification constant of the PHP output handler.

PHP_OUTPUT_HANDLER_CONT: PHP output processing continuation identification constant.

PHP_OUTPUT_HANDLER_END: ​​The end identification constant of the PHP output handler.

These are some common PHP built-in constants, which can be used directly in PHP scripts without prior definition. By using these constants, you can easily obtain some information related to the PHP parser and the current environment.

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