生成uid的算法

private function _getUid()
{
//2013-01-01 00:00:00 (timestamp-microtime)
$startTime= 1356969600000;
$preBit = '0'.decbin(intval(microtime(1) * 1000) - $startTime);
$partitionNumber = '0000000000';
$counter = decbin(rand(0, 4096));
return bindec($preBit.$partitionNumber.$counter);
}