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)));
?>