Question

There are two arrays that need to be changed within a function.
How to pass that arrays?
The way I know is to declare 2 arrays as global variables within a function:

function myfunc(){
 global $arr1;
 global $arr2;
 //do something
}

Does it make sense and is it possible to pass two arrays as references instead? How (in case if Yes)?

Answer 1

Here is how you can pass them by reference, define your function as follows:

function myfunc(&$arr1, &$arr2) {
    // ... modify arrays here
}

Just prepend the function arguments you want passed by reference with an &. Now when they are received by the function, they are references.

You do not have to (and should not) put the & in front of the variables when you are calling the function as this results in a call-time pass-by-reference notice. Just pass them to your function as usual $res = myfunc($first, $second);

See Passing by Reference