what does mean array($this, $some_method_string )?

php arrays methods

array($this, $some_method_string)

it is a valid callback , calling the method $some_method_string on $this :

with array_map , for every element of $some_data , call $this->$some_method_string(currentElement)

php arrays methods

You have a function with a name, e.g. function my_function ....

You have to give the name of that function as a string or string variable.

CodeHunter