php (6) PHP constants

1. Custom constants

* Must be defined using the function define()

* After definition, its value cannot be changed

* Use the constant name directly when using it. You cannot add $s

in front like a variable. For example: define("PI",3.14); define a constant

$area = PI*R* R; Calculate the area of ​​a circle

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

echo "My URL is:".URL;

2 System constants:

FILE: php program file name

LINE: The number of lines of PHP program files

PHP_VERSION: The version number of the current parser

PHP_OS: The name of the operating system that executes the current PHP version

__FILE__ The name of the script file currently being processed.

__LINE__ The current line number of the script file currently being processed, the same as before.

TRUE represents true value.

FALSE represents a false value (false).

E_ERROR This constant points to the most recent error.

E_WARNING This quantity refers to the nearest warning.

E_PARSE This constant is a potential problem in parsing grammar.

The above is the content of php (6) PHP constants. For more related content, please pay attention to the PHP Chinese website (www.php.cn)!