在MongoDB中模拟Auto Increment的php代码

<?php
function generate_auto_increment_id($namespace, array $option = array())
{
$option += array(
'init' => 1,
'step' => 1,
);
$instance = new mongo();
$instance = $instance->selectcollection('_seq', 'seq');
$seq = $instance->db->command(array(
'findandmodify' => 'seq',
'query' => array('_id' => $namespace),
'update' => array('$inc' => array('id' => $option['step'])),
'new' => true,
));
if (isset($seq['value']['id'])) {
return $seq['value']['id'];
}
$instance->insert(array(
'_id' => $namespace,
'id' => $option['init'],
));
return $option['init'];
}
var_dump(generate_auto_increment_id('foo'));
var_dump(generate_auto_increment_id('bar', array('init' => 123)));
?>