How to compare two DATETIMEs from MySQL

Question

I want to limit my users to only (be able to) post something every 15 minutes.

So in my SQL query I select NOW() to get the current date and time, and also the user's last post date date_added. I want to compare the two dates and if the difference between now() and date_added is less than 15 minutes, then the user cannot yet post. If it's greater then he can. If less than 15 minutes then I'd like a message like 'Please wait x minutes and y seconds.' So I need some kind of date manipulation/comparison.

How should I approach this. In MySQL or PHP?

Answer 1

In MySQL: DATE_ADD() or DATE_SUB(), then compare.

In PHP: DateTime->diff().

Answer 2

You could simply convert the mysql timestamp into a php-date and compare from there $time = date ("Y-m-d H:i:s", $mysqltime);

You will find lots of useful snippets how to compare dates on the functions documentation: http://php.net/manual/de/function.date.php

Edit: pozs anwser nails it ...

Answer 3

Something like

SELECT count(*) FROM posts WHERE last_post > DATE_SUB(NOW(), INTERVAL 15 minute);