define
Defines a named constant at runtime.
Parameters
- constant_name
-
The name of the constant.
Note:
It is possible to define constants with reserved or even invalid names, whose value can (only) be retrieved with constant. However, doing so is not recommended.
- value
-
The value of the constant. In PHP 5, value must be a scalar value (int, float, string, bool, or null). In PHP 7, array values are also accepted.
Warning:
While it is possible to define resource constants, it is not recommended and may cause unpredictable behavior.
- case_insensitive
-
If set to true, the constant will be defined case-insensitive. The default behavior is case-sensitive; i.e. CONSTANT and Constant represent different values.
Warning:
Defining case-insensitive constants is deprecated as of PHP 7.3.0. As of PHP 8.0.0, only false is an acceptable value, passing true will produce a warning.
Note:
Case-insensitive constants are stored as lower-case.
Return Values
Returns true on success or false on failure.
Changelog
| Version | Description |
| 8.0.0 | Passing true to case_insensitive now emits an E_WARNING. Passing false is still allowed. |
| 7.3.0 | case_insensitive has been deprecated and will be removed in version 8.0.0. |
| 7.0.0 | array values are allowed. |