Accessing object properties within a callback execution - php

Question

Let's say I have the following code:
class RandomNumber{
public $number;
function __construct($range,$callback){
$this->number = rand(0,$range);
$callback();
}
}
$rnd = new RandomNumber(9,function(){
echo "Line 11: ".$rnd->number."\n"; // Not working: empty variable
echo "Line 12: ".$number."\n"; // Not working: empty variable
echo "Line 13: ".$this->number."\n"; // Not working: Fatal error: Using $this when not in object context on line 13
});
echo "Line 15: ".$rnd->number."\n"; // Working: echoed random number
So I'm trying to access the property (number) of the newly created object. And I can not guess how to do it properly. I have read some PHP documentation and tried to search Google for the solution but I missed the thing or I used wrong keywords for searching. I'd be happy if you will point me into the right direction.

Answer 1

It's barely possible, because the things are happening one after the another, as well as the function is not aware of the outside world. In your case $rnd is declared outside the function as well as it's not already initialized (it will be after the whole line is executed)
And yes, you are not able to use $this, but you can pass $this in order to inject the newly created object.
class RandomNumber{
public $number;
function __construct($range,$callback){
$this->number = rand(0,$range);
$callback($this);
}
}
$rnd = new RandomNumber(9,function($obj){
echo "Line 11: ".$obj->number."\n";
});

Answer 2

You define the function outside of the scope of the class, inside of it it works just fine.
And $rnd cant work inside of it, as it is not yet filled, this will happen after the constructor did its work.
This works:
class RandomNumber{
public $number;
function __construct($range,$callback){
$this->number = rand(0,$range);
$callback($this);
$call2 = function(){
echo "Line 7 : " .$this->number."\n"; // Works
};
$call2();
}
public function callback($callback){
$callback();
}
}
$rnd = new RandomNumber(9,function($rnd){
echo "Line 15: ".$rnd->number."\n"; // Works
});
$rnd->callback(function() use ($rnd) {
echo "Line 19: ".$rnd->number."\n"; // Works
});