Class Constructor Interfering With Another Class

Question

Essentially, I am just creating two classes where one class, in this case class A, runs a function in another class, in this case class B, to grab some information from the database. However, when the `B_runtime()` actually calls upon the database I get the error `Cannot access protected property A::$db`. What I don't understand is that even though I have two `__construct`'s in both classes the PDO statement is being very persistent on using the database connection from class A. I am sure this has something to do with the fact that I am running the `B_runtime()` from within class A because this doesn't happen if I call it from outside of class A. I know that I can simply change the `protected $db;` in class A to a public variable, however, I am really curious as to how I can fix this. ``` ob_start(); include('/config.php'); ob_end_clean(); $A = new A($db); $B = new B($db); echo $A->A_runtime(); class A{ protected $db; public function __construct($db){ $this->db = $db; } public functio…

Accepted Answer

You could pass the instance of B to the method. This way you also define the dependancy of your method on class B.

```
$A = new A($db);
$B = new B($db);

echo $A->A_runtime($B);

class A{
    //...
    public function A_runtime($instance){
        return $instance -> B_runtime();      
    }
}
```

You can even use type hinting in PHP 5 to signal that you are expecting an instance of class B there:

```
    public function A_runtime(B $instance){
```

Class Constructor Interfering With Another Class

Solution

Problem