Filtering a Traversable object using PHP SPL filtering capabilities in response to http://www.dragonbe.com/2015/07/speeding-up-database-calls-with-pdo-and.html

filtering-pdostatement.php

<?php

$pdo = new \PDO(
    $config['db']['dsn'],
    $config['db']['username'],
    $config['db']['password']
);

$sql  = 'SELECT * FROM `gen_contact` ORDER BY `contact_modified` DESC';
$stmt = $pdo->prepare($sql);
$stmt->setFetchMode(\PDO::FETCH_OBJ);
$stmt->execute();

$convertToIterator = function (\Traversable $traversable) {
    foreach ($traversable as $row) {
        yield $row;
    }
};

$condition = '2015-04-01 00:00:00';
$filterLastPeriod = function ($row) use ($condition) {
    return (new \DateTime($condition))->format('Y-m-d').' 00:00:00' < $row->contact_modified;
};

foreach (new \CallbackFilterIterator($convertToIterator($stmt), $filterLastPeriod) as $row) {
    var_dump($row); //do something meaningfull with the filtered rows
}