Javascript debugger
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defined
Checks whether a given named constant exists
(PHP 4, PHP 5)
bool defined ( 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().
Examples
Example 1353. 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;
}
?>
See Also
| define() |
| constant() |
| get_defined_constants() |
| function_exists() |
| The section on Constants |