In PHP, expressions cannot be used as constant values because they are not scalar types. The constant must be a valid identifier and its value must be an integer, float, string, or boolean.
What in PHP cannot be used as a constant value?
In PHP, what cannot be used as a constant value is anexpression.
Constants are defined in PHP using thedefine()
function, which requires providing a name and a value. The constant name must be a valid identifier and the value must be a scalar type (integer, float, string, or boolean).
Expressions cannot be used as constant values because they are not scalar types. An expression can compute or operate on a value, but is not itself a value.
For example, the following declaration is invalid because it uses an expression (2 3
) as a constant value:
define('MY_CONSTANT', 2 + 3);
In contrast, the following declaration is valid because it A scalar value (5
) is used as the constant value:
define('MY_CONSTANT', 5);
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