Php (6) PHP constants

Php (6) PHP constants 1. Custom constants

* Must be defined using the define () function

* After definition, the value cannot be changed.

* The constant name is used directly. you cannot add $ s in front of a variable.

For example: define ("PI", 3.14); defines a constant

$ Area = PI * R; calculate the area of the circle

Define ("URL", "http://www.youbml.com ");

Echo "My website is:". URL;

2 System constants:

FILE: php program FILE name

LINE: Number of PHP program files

PHP_VERSION: version number of the current parser

PHP_ OS: name of the operating system for executing the current PHP version

_ FILE _ the script FILE name being processed.

_ LINE _ current number of rows of the script file being processed, same as the previous number.

TRUE indicates the true value (TRUE ).

FALSE indicates a pseudo value (false ).

The constant E_ERROR indicates the most recent error.

E_WARNING refers to the nearest warning.

E_PARSE this constant is a potential problem with the parsing syntax.

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