在PHP中的构造函数中初始化类常量

Question

Just like in C++ is it possible to initialize class constant in the constructor?

Similar to C++ it'd look like:

class Abc
{
    const WIDTH;

    public __constructor($width):WIDTH($width) //WIDTH gets assigned here and is immutable
    {
        //I know syntax may not be ok but is anything similar possible in PHP?
    }

}

Answer 1

No, this is not possible in PHP. A constant's value must be defined when you define the constant, and it must be a constant expression.

Not recommended: Of course, if runkit is installed, you can use runkit_constant_add():

public function __construct($width)
{
    runkit_constant_add(__CLASS__ . '::WIDTH', $width);
}