defined — Checks whether a given named constant exists
Description
booldefined
( string$name
)
Checks whether the given constant exists and is defined.
Note:
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().
Parameters
name
The constant name.
Return Values
Returns TRUE if the named constant given by name
has been defined, FALSE otherwise.
Examples
Example #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; } ?>
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