New expressions are not supported in this context

Description

It is not possible to use directly an object as value for a class constant.

It is also not allowed to use an object as default value for properties, static or not.

On the other hand, it is possible to use an object stored in a global constant. And, since it is possible to use a global constant as a value for a class constant, it is easy to work around this limitation. The same trick is possible with properties, as long as the target object is not self.

Properties cannot use their host class as default values: it leads to a chicken and egg problem. The global constant must be created with an object of the class, which is then immediately instantiated with a default value based on the global constant.

Example

<?php

class B {}

const CONSTANT_B = new B;

class x {
     // This is not possible
     const A = new B;

     // This is possible, with the same result
     const A2 = CONSTANT_B;
}

?>

Solutions

• Remove the constant A.

• Create a global constant, and assign it to A.

• Make the constant a property.

• Create a global constant, and assign it to the class constant.