PHP时间戳记，今天向用户显示在线

Question

I had a function working which showed me users that have visited my website today, there is a field in a MYSQL database called 'lastvisit'.

I use to use a MYSQL time stamp however server time was different to my local time, so didn't work properly.

I know set the time zone in PHP and store the date and time as a VARCHAR in the database, like:

date_default_timezone_set('UTC');
$visittime = date('jS M Y H:i A');

//Update timestamp to show latest visit
$sql="UPDATE users SET lastvisit='$visittime' where email ='$email' ";


29th Jan 2013 22:29 

How can I write a PHP function to show users that have been online today, and the amount of users online within the last 24 hours.

Answer 1

This will do the job if you will be doing it in MySQL assuming that you want to count distinct email . ( much better if you can use the primary key of the user. )

This will return total count of users online yesterday and today.

SELECT  DATE(STR_TO_DATE(lastvisit, '%D %b %Y %H:%i')), 
        COUNT(DISTINCT email)
FROM    users
WHERE   DATE(STR_TO_DATE(lastvisit, '%D %b %Y %H:%i')) BETWEEN CURDATE + INTERVAL -1 DAY AND CURDATE()
GROUP   BY DATE(STR_TO_DATE(lastvisit, '%D %b %Y %H:%i'))