These functions check the status of a variable, change its type, or return a value as a particular data type.
The define function creates a constant, which is essentially a variable that may be set only once. The value argument may be a string, integer, double, or boolean. It may not be an array or object. The non_case_sensitive argument is optional. By default, constants are case sensitive, which is the same as with variables.
If the constant cannot be created for some reason, FALSE will be returned. If you wish to check that a constant is defined, use the defined function.
It is customary to name constants using all uppercase letters, as is the ...