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php恒量define()constant(),defined()

时间:2021-07-01 10:21:17 帮助过:29人阅读

php常量 define() constant() , defined()

define――定义常量,若定义true,则读取时不区分大小写

bool define( string name, mixed value [, bool case_insensitive])

常量只能包含标量数据(booleanintegerfloatstring )。

define ( "CONSTANT" , "Hello world." );
echo
CONSTANT ; // outputs "Hello world."
echo Constant ; // outputs "Constant" and issues a notice.

define ( "GREETING" , "Hello you." , true );
echo
GREETING ; // outputs "Hello you."
echo Greeting ; // outputs "Hello you."

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constant()――读取常量

mixed constant ( string name)

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define ( "MAXSIZE" , 100 );

echo
MAXSIZE ;
echo
constant ( "MAXSIZE" ); // same thing as the previous line

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defined――判断常量是否定义

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bool defined ( string name)

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if ( defined ( 'CONSTANT' )) {
????echo
CONSTANT ;
}

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预定义常量

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__FILE__?? 取得文件的物理地址? 注:左右各2条下划线

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echo __FILE__? ?? //C:\wamp\www\T1\1.php

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