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php自定义全局常量与类常量

/**
 * 1、define(name,value,case_insensitive) 自定义全局常量, 默认大小写敏感
 * 2、const 定义类常量。
 * 3、常量名前不要使用”$”
 * 4、常量的命名一般全部使用大写字母。
 */
//定义全局常量 LANGUAGE
define('LANGUAGE','中国');
echo language;//language
echo LANGUAGE;//中国

//定义全局常量 CN
define('CN','中国',TRUE);
echo CN;//中国
echo cn;//中国

//定义类常量
class ConstTest{
	const VERSION = '1.0';
	function ConstTest(){
		//类内部使用“self::常量名”调用,不能使用$this
		echo 'self::VERSION='.self::VERSION;
	}
}
//实例化 ConstTest,目的是调用构造函数
new ConstTest();

//外部调用类常量,通过“类名::常量名”直接调用,无需实例化。
echo 'VERSION='.(ConstTest::VERSION);


echo '<br>';
//array get_defined_constants ([ bool $categorize = false ] ) 返回所有已定义的常量
//print_r(get_defined_constants(true));

//bool defined ( string $name ) 检查该名称的常量是否已定义。
echo defined('cn')?'true':'false';

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打印结果:

language
中国
中国
中国
self::VERSION=1.0
VERSION=1.0
true

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http://huangqiqing123.iteye.com/blog/1921428

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