日志记录：在多个类中使用相同的对象

Question

I've been sitting on this for ages now and cannot figure out a way that satisfies me.

My problem: I got a parent class and various subclasses. In the constructor of the parent, a new object is created (amongst other things). This object is from my log file class. It is stored in a protected variable.

In the parent class, the log keeping is not a problem, everything is done according to plan.

If I want to use the object in a subclass, I cant get it to work. I just cant access it. I tried a function in the parent class in order to return the object, this didnt work either.

I am at a loss here.

This is the constructor of the parent:

function __construct() {
...   
 $this->reg_log_file = new log_file(bef_registration::REG_LOG_NAME, bef_registration::REG_LOG_KEEPING);
...
}

In order to create a new entry, in the parent class, the following is sufficient:

$this->reg_log_file->entry('start log');

In a child class, this would lead to an error:

Call to a member function entry() on a non-object

After googling and reading for hours, I still havent come up with a proper way of doing this.

Anyone with an idea?

Answer 1

You should run parent::__construct(); in the body of every child contstructor and the log object will be instantiated and visible in all inherited subclasses.