Description:
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I made a class which implements ArrayAccess. Then I try to use foreach on one of its array values and I get error "Objects used as arrays in post/pre increment/decrement must return values by reference"

I've reduced the big code fragment to this small one:

Reproduce code:
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<?
class foo implements ArrayAccess {
	protected $params;			
	public function offsetGet ($field) { return $this->params[$field]; }
	public function offsetExists ($field) { return isset ($this->params[$field]); }	
	public function offsetUnset ($field) { unset ($this->params[$field]); }
	public function offsetSet ($field, $value) { $this->params[$field] = $value; }	
}

$foo = new foo;
foreach ($foo['options'] as $optionvalue => $optiontext) {}


Expected result:
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no errors

Actual result:
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Fatal error: Objects used as arrays in post/pre increment/decrement must return values by reference in ... on line 161