如何在PHP OOP中将变量放入变量？ [关闭]

Question

My code is like that

class Some extends Another {
    var $first = "Hello";
    var $second = "Hello";
}

I want to put $first to $second so how I can put it? I try something like the following

class Some extends Another {
    var $first = "Hello";
    var $second = "Hello $first";
}

but I got the following errors

syntax error, unexpected '"'

And it's that possible to put?

Answer 1

I don't believe you can reference class members like that - you would have to set up $second in the constructor:

class Some
{
    public $first = "Hello";
    public $second;

    public function __construct()
    {
        $this->second = "Hello {$this->first}";
    }
}

Though a more realistic way to approach this particular example would be like so:

class Some
{
    public $first = 'Marty';

    public function getSecond()
    {
        return "Hello {$this->first}";
    }
}