PHP An iterator cannot be used with foreach by reference - php

Question

I have an object that implements Iterator and holds 2 arrays: "entries" and "pages". Whenever I loop through this object, I want to modify the entries array but I get the error An iterator cannot be used with foreach by reference which I see started in PHP 5.2.
My question is, how can I use the Iterator class to change the value of the looped object while using foreach on it?
My code:
//$flavors = instance of this class:
class PaginatedResultSet implements \Iterator {
private $position = 0;
public $entries = array();
public $pages = array();
//...Iterator methods...
}
//looping
//throws error here
foreach ($flavors as &$flavor) {
$flavor = $flavor->stdClassForApi();
}
The reason for this is that sometimes $flavors will not be an instance of my class and instead will just be a simple array. I want to be able to modify this array easily regardless of the type it is.

Answer 1

I just tried creating an iterator which used:
public function &current() {
$element = &$this->array[$this->position];
return $element;
}
But that still did not work.
The best I can recommend is that you implement \ArrayAccess, which will allow you to do this:
foreach ($flavors as $key => $flavor) {
$flavors[$key] = $flavor->stdClassForApi();
}
Using generators:
Updating based on Marks comment on generators, the following will allow you to iterate over the results without needing to implement \Iterator or \ArrayAccess.
class PaginatedResultSet {
public $entries = array();
public function &iterate()
{
foreach ($this->entries as &$v) {
yield $v;
}
}
}
$flavors = new PaginatedResultSet(/* args */);
foreach ($flavors->iterate() as &$flavor) {
$flavor = $flavor->stdClassForApi();
}
This is a feature available in PHP 5.5.

Answer 2

Expanding upon Flosculus' solution, if you don't want to reference the key each time you use the iterated variable, you can assign a reference to it to a new variable in the first line of your foreach.
foreach ($flavors as $key => $f) {
$flavor = &$flavors[$key];
$flavor = $flavor->stdClassForApi();
}
This is functionally identical to using the key on the base object, but helps keep code tidy, and variable names short... If you're into that kind of thing.

Answer 3

If you implemented the iterator functions in your calss, I would suggest to add another method to the class "setCurrent()":
//$flavors = instance of this class:
class PaginatedResultSet implements \Iterator {
private $position = 0;
public $entries = array();
public $pages = array();
/* --- Iterator methods block --- */
private $current;
public function setCurrent($value){
$this->current = $value;
}
public function current(){
return $this->current;
}
//...Other Iterator methods...
}
Then you can just use this function inside the foreach loop:
foreach ($flavors as $flavor) {
$newFlavor = makeNewFlavorFromOldOne($flavor)
$flavors -> setCurrent($newFlavor);
}
If you need this function in other classes, you can also define a new iterator and extend the Iterator interface to contain setCurrent()