PHP. Руководство по PHP. 2005

defined

Пред.

След.

defined

(PHP 3, PHP 4, PHP 5)defined -- Checks whether a given named constant exists

Description

bool defined (string name)

Returns TRUE if the named constant given by name has been defined, FALSE otherwise.

Пример 1. Checking Constants


<?php
/* Note the use of quotes, this is important. This example is checking
* if the string 'CONSTANT' is the name of a constant named CONSTANT */
if (defined('CONSTANT')){
echo CONSTANT;
}
?>

Замечание: If you want to see if a variable exists, use isset() as defined() only applies to constants. If you want to see if a function exists, use function_exists().

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