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# defined

(PHP 3 <= 3.0.18, PHP 4 >= 4.0.0)

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.

Example 1. Checking Constants
    <?php
    if (defined("CONSTANT")){ // Note that it should be quoted
        echo CONSTANT; //
        }
    ?>

See also define(), constant() and the section on Constants.

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