La interfaz IteratorAggregate

<?php

class myData implements IteratorAggregate
{
    public function getIterator(): Traversable
    {
        return new ArrayIterator([
            "clave uno" => "elemento uno",
            "clave dos" => "elemento dos",
            "clave tres" => "elemento tres"
        ]);
    }
}

$obj = new myData();

foreach($obj as $key => $value) {
    var_dump($key, $value);
    echo "\n";
}

string(9) "clave uno"
string(12) "elemento uno"

string(9) "clave dos"
string(12) "elemento dos"

string(10) "clave tres"
string(13) "elemento tres"