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constant

constant

(PHP 4 >= 4.0.4, PHP 5)

constantReturns the value of a constant

说明

mixed constant ( string $name )

Return the value of the constant indicated by name.

constant() is useful if you need to retrieve the value of a constant, but do not know its name. I.e. it is stored in a variable or returned by a function.

This function works also with class constants.

参数

name

The constant name.

返回值

Returns the value of the constant, or NULL if the constant is not defined.

错误/异常

An E_WARNING level error is generated if the constant is not defined.

范例

Example #1 constant() example

<?php

define
("MAXSIZE"100);

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


interface bar {
    const 
test 'foobar!';
}

class 
foo {
    const 
test 'foobar!';
}

$const 'test';

var_dump(constant('bar::'$const)); // string(7) "foobar!"
var_dump(constant('foo::'$const)); // string(7) "foobar!"

?>

参见


  • connection_aborted
  • connection_status
  • connection_timeout
  • constant
  • define
  • defined
  • die
  • eval
  • exit
  • highlight_file
  • highlight_string
  • ignore_user_abort
  • pack
  • php_check_syntax
  • php_strip_whitespace
  • show_source
  • sleep
  • sys_getloadavg
  • time_nanosleep
  • time_sleep_until
  • uniqid
  • unpack
  • usleep
  • __halt_compiler
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