PHP. Руководство по PHP. 2005

Creating Constants Пред.

Глава 53. Creating Variables

Creating Constants

Zend supports the creation of true constants (as opposed to

regular variables). Constants are accessed without the typical

dollar sign ($) prefix and are available in all

scopes. Examples include TRUE and

FALSE, to name just two.

To create your own constants, you can use the macros in

All the macros create a constant with the specified name and value.

You can also specify flags for each constant:

CONST_CS - This constant's name is to be

treated as case sensitive.

CONST_PERSISTENT - This constant is

persistent and won't be "forgotten" when the current process

carrying this constant shuts down.

To use the flags, combine them using a inary OR:

// register a new constant of type "long"
REGISTER_LONG_CONSTANT("NEW_MEANINGFUL_CONSTANT", 324, CONST_CS |
CONST_PERSISTENT);

There are two types of

macros - REGISTER_*_CONSTANT

andREGISTER_MAIN_*_CONSTANT. The first type

creates constants bound to the current module. These constants are

dumped from the symbol table as soon as the module that registered

the constant is unloaded from memory. The second type creates

constants that remain in the symbol table independently of the

module.

Таблица 53-6. Macros for Creating Constants

Macro	Description
REGISTER_LONG_CONSTANT(name, value, flags) REGISTER_MAIN_LONG_CONSTANT(name, value, flags)	Registers a new constant of type long.
REGISTER_DOUBLE_CONSTANT(name, value, flags) REGISTER_MAIN_DOUBLE_CONSTANT(name, value, flags)	Registers a new constant of type double.
REGISTER_STRING_CONSTANT(name, value, flags) REGISTER_MAIN_STRING_CONSTANT(name, value, flags)	Registers a new constant of type string. The specified string must reside in Zend's internal memory.
REGISTER_STRINGL_CONSTANT(name, value, length, flags) REGISTER_MAIN_STRINGL_CONSTANT(name, value, length, flags)	Registers a new constant of type string. The string length is explicitly set to length. The specified string must reside in Zend's internal memory.

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