从PHP获取时间戳

I am trying to get the timestamp in php. Using following code

$date = new DateTime();
        echo $date->getTimestamp();

error comes getTimestamp() is undefined however according to this

http://php.net/manual/en/datetime.gettimestamp.php

I need the format like 123456789

Note the PHP 5 >= 5.3.0 on the doc page. I can only assume you're using a version pre-5.3, therefore:

echo time(); //output: 1358796864

Make sure you are running PHP 5.3 or newer. It doesn't work in PHP 5.2 or older

Perhaps this would be helpful: http://php.net/manual/en/function.date.php