How do you perform inner joins with xPDO

// Sample snippet to illustrate inner joins with xPDO.
// Make sure you've created some records in the person, phone and person_phone tables.

global $modx;
include_once ($modx->config['base_path'].'assets/snippets/' . 'xpdo/xpdo.class.php');
include_once ($modx->config['base_path'].'assets/snippets/' . 'xpdo/table/maketable.class.php');
// set these as appropriate
$xpdo= new xPDO('mysql:host=localhost;dbname=modx', "dbuser", "password");
$xpdo->setPackage('sample');

$people = array ();
$personTbl = $xpdo->getTableName('Person');
$phoneTbl= $xpdo->getTableName('Phone');
$ppTbl = $xpdo->getTableName('PersonPhone');
$personColumns= $xpdo->getSelectColumns('Person', 'p');
$phoneColumns= $xpdo->getSelectColumns('Phone', 'ph');
$ppColumns = $xpdo->getSelectColumns('PersonPhone', 'pp');

if ($stmt= $xpdo->prepare("SELECT $personColumns,$phoneColumns,$ppColumns FROM $personTbl AS p, $phoneTbl AS ph, $ppTbl AS pp WHERE p.id=pp.person AND ph.id=pp.phone")) {
    if ($stmt->execute()) {
        foreach ($stmt->fetchAll(PDO_FETCH_ASSOC) as $row) {
            $person= $xpdo->newObject('Person');
            $person->fromArray($row, '', true);
            $phone= $xpdo->newObject('Phone');
            $phone->fromArray($row, '', true);
            $personPhone = $xpdo->newObject('PersonPhone');
            $personPhone->fromArray($row, '', true);
            $personPhone->addOne($phone);
            $person->addMany($personPhone);
            $people[]= $person;
        }
    }
}

$table = new MakeTable($xpdo);
$tableData = false;

foreach($people as $person)
{
	$ppSet = $person->getMany('PersonPhone');

	foreach ($ppSet as $pp)
	{
		$number = $pp->getOne('Phone');
		$tableData[] = array('name' => $person->get('first_name') . ' ' . $person->get('last_name'),
                            'dob' => $person->get('dob'), 'number' => $number->get('number'));
	}
}

return $table->create($tableData);

<?php 
$person = $xpdo->getObject('Person', 1);	// get the Person object with primary key value == 1
$pps = $person->getMany('PersonPhone');		// get all PersonPhone objects related to this Person
$phone;					// declare this here so we can use it after the foreach loop
foreach ($pps as $k => $v)		// loop on each PersonPhone object
{
	$phone = $v->getOne('Phone');		// get the Phone object related to this PersonPhone
	// do what you want here, e.g. find a phone number with a given id passed in via a GET variable
	if ($phone->get('id') == $_GET['id'])
		break;
}

// do stuff with $phone...
?>

<?php
$person= $xpdo->getObjectGraph('Person', '{PersonPhone:{id:{Phone:{phone:{}}}}}', 1);

<?php
$xpdo->config['hydrate_rel_obj_vars']= true;
$person_id= 1;
$phone_id= 1;
$person= $xpdo->getObjectGraph(
    'Person', 
    '{PersonPhone:{id:{Phone:{phone:{}}}}}', 
    array ('Person.id' => $person_id, 'PersonPhone.phone' => $phone_id)
);
$compoundKey= $person_id . '-' . $phone_id;
$phone= & $person->PersonPhone[$compoundKey]->Phone;
if ($phone) {
    print_r($phone->toArray());
    // ... do stuff with just the specific $phone we wanted ...
}