gistfile1.php

<?php
$pdo = new PDO('sqlite::memory:');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$pdo->exec('CREATE TABLE foo (bar VARCHAR(20))');
$sth = $pdo->prepare('INSERT INTO foo (bar) VALUES (:bar)');
var_dump($sth);
$sth->execute(array('bar' => 'bar'));
$sth->execute(array('bar' => null));

$sth = $pdo->prepare('SELECT * FROM foo');
$sth->execute($bind);
$rows = $sth->fetchAll(PDO::FETCH_ASSOC);
var_dump($rows);

array(2) {
  [0]=>
  array(1) {
    ["bar"]=>
    string(3) "bar"
  }
  [1]=>
  array(1) {
    ["bar"]=>
    NULL
  }
}