PHP foreach parameter coercion problem_PHP tutorial

class service implements Iterator{
function __construct( $service_define,$filter=null){
$this->iterator = new ArrayIterator($service_define['list']);
$this->filter = $filter;
$this- >valid();
}
function current(){
return $this->current_object;
}
public function rewind() {
$this-> iterator->rewind();
}
public function key() {
return $this->iterator->current();
}
public function next() {
return $this->iterator->next();
}
public function valid() {
while($this->iterator->valid()){
if($this->filter()){
return true;
}else{
$this->iterator->next();
}
};
return false;
}
private function filter(){
$current = $this->iterator->current();
if($current){
$this->current_object = new Sameple($current);
if($this->current_object){
return true;
}
}
return false;
}
}
class Sameple{
var $class_name;
function __construct($class_name = null) {
$this->class_name = $class_name;
}
function show(){
echo $this->class_name,'
';
}
}
$servicelist = array(
'list' = > array(
'first',
'second',
'third',
'fourth',
),
);
$ser = new service ($servicelist);
foreach ($ser as $s) {
$s->show();
}
/*
//The code to execute the error report uses $ser performs cast operation
foreach ((array)$ser as $s) {
$s->show();
}*/