PHP Object Iteration
PHP provides a way for objects to be defined so it is possible to iterate through a list of items, for example with a foreach statement.
1. Simple Iteration
By default, all visible properties will be used for the iteration.
class MyClass {
public $var1 = 'value 1';
public $var2 = 'value 2';
public $var3 = 'value 3';
protected $protected = 'protected var';
private $private = 'private var';
function iterateVisible() {
echo "MyClass::iterateVisible:\n";
foreach ($this as $key => $value) {
print "$key => $value\n";
}
}
}
$class = new MyClass();
foreach($class as $key => $value) {
print "$key => $value\n";
}
echo "\n";
$class->iterateVisible();2. The Iterator Interface
To customize object iteration, you can implement the Iterator interface. It requires 5 methods:
current(): Returns the current element.key(): Returns the key of the current element.next(): Moves forward to next element.rewind(): Rewinds the Iterator to the first element.valid(): Checks if current position is valid.
class myIterator implements Iterator {
private $position = 0;
private $array = array(
"firstelement",
"secondelement",
"lastelement",
);
public function __construct() {
$this->position = 0;
}
public function rewind(): void {
$this->position = 0;
}
public function current(): mixed {
return $this->array[$this->position];
}
public function key(): mixed {
return $this->position;
}
public function next(): void {
++$this->position;
}
public function valid(): bool {
return isset($this->array[$this->position]);
}
}
$it = new myIterator;
foreach($it as $key => $value) {
var_dump($key, $value);
}3. IteratorAggregate
Alternatively, you can implement the IteratorAggregate interface, which requires just one method getIterator(). This is often easier if you just want to return an array iterator or a generator.
class MyCollection implements IteratorAggregate {
private $items = [1, 2, 3];
public function getIterator(): Traversable {
return new ArrayIterator($this->items);
}
}