defined
Description
The defined of Miscellaneous for PHP checks whether a given named constant exists.
Syntax
defined(
string $constant_name
): boolParameters
constant_name
The constant name.
Return
Returns true if the named constant given by constant_name has been defined, false otherwise.
Examples
1 · constant_name · false
<? $constant_name = "MYCONSTANT"; $return = defined($constant_name); var_export($return); ?>
false
2 · constant_name · true
<? $constant_name = "MYCONSTANT"; $value = "string"; define($constant_name, $value); $return = defined($constant_name); var_export($return); ?>
true
