How to call a method of another class inside a method of one class in php?

Question

PHP

There are classes:

class DataBase{
  public function name1(){
    //
  }
}
class User(){
  public function name2(){
    // Здесь нужно вызвать метод name1() из класса DataBase
  }
}

I try:

protected $db;
    public function __constructor(DataBase $DB)
    {
        $this->db = $DB;
    }
  public function name2(){
    $this->db->name1();
  }

Error:
Call to a member function name1() on null in...
Only works if I initialize the class inside the name2() method.

Answer 1

https://ideone.com/yQMST1

Answer 2

It says to you: Call to a member function name1() on null , which means that the $this->db field has the value $this->db . $this->db , for you, the value from the $DB parameter is initialized in the class constructor . This means that $DB is also null . And now think about why null is passed to your class instead of an object of the DataBase class .