Mysqli and generator are in a boat...

gistfile1.php

<?php

namespace db;

class client
{
	private
		$user,
		$password,
		$host,
		$port,
		$mysqli
	;

	function __construct($user = '', $password = '', $host = 'localhost', $port = 3306)
	{
		$this->user = $user;
		$this->password = $password;
		$this->host = $host;
		$this->port = $port;
	}

	function execute($query)
	{
		if (! $this->mysqli)
		{
			$mysqli = new \Mysqli($this->host, $this->user, $this->password, '', $this->port);

			if ($mysqli->connect_errno)
			{
				throw new \runtimeException('Unable to connect');
			}

			$this->mysqli = $mysqli;
		}

		$result = $this->mysqli->query($query);

		if ($result === false)
		{
			throw new \runtimeException('Unable to execute \'' . $query . '\'');
		}

		return new result($this->mysqli->affected_rows, $result === true ? null : function() use ($result) {
				$result->data_seek(0);

				$key = 0;

				while ($record = $result->fetch_assoc())
				{
					yield $key++ => $record;
				}
			}
		);
	}
}

final class result implements \iteratorAggregate
{
	private
		$rows,
		$generator
	;

	function __construct($rows, callable $generator = null)
	{
		$this->rows = $rows;
		$this->generator = $generator ?: function() { yield; };
	}

	function __get($property)
	{
		if ($property == 'rows')
		{
			return $this->rows;
		}

		throw new \logicException('Undefined property: ' . $property);
	}

	function __set($property, $value)
	{
		throw new \logicException(get_class($this) . ' is immutable');
	}

	function __unset($property)
	{
		throw new \logicException(get_class($this) . ' is immutable');
	}

	function __isset($property)
	{
		return $property == 'rows';
	}

	function getIterator()
	{
		return call_user_func($this->generator);
	}
}

$result = (new client('root', 'qwjkuio3'))->execute('SELECT 1');

var_dump($result->rows);

foreach ($result as $record1)
{
	$record1 = '1. ' . $record1[1];

	foreach ($result as $record2)
	{
		var_dump($record1 . PHP_EOL . '2. ' . $record2[1]);
	}
}