PHP compare dates

Question

Possible Duplicate:
php date compare

I have a date that I take from the mySQL database that looks like this:

2011-06-20

And I get the date of the current day in this way:

$todaydate = date('Y-m-d');

What I need to know is how do I compare the two results?

How can I compare the dates and understand for example if a week is passed from the database date or a month or a year..etc..?

Thank you!!

kba · Accepted Answer · 2011-06-20T00:56:42.300

There is no need to put that burden on PHP when MySQL has built-in functionality for that already. You should take a look at MySQL's DATEDIFF() function:

DATEDIFF() returns expr1 – expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions. Only the date parts of the values are used in the calculation.

An example of two dates that'd give a 7-day difference could be:

mysql> select datediff('2011-06-18','2011-06-25');
+-------------------------------------+
| datediff('2011-06-18','2011-06-25') |
+-------------------------------------+
|                                  -7 | 
+-------------------------------------+

This means that the first date occured -7 days after the first date; that's 7 days before. If you let the two arguments switch place, the result would be a positive 7.

Could you provide an example? For example for 7 days difference? I do not really know where to start! Thank you! — DiegoP., Jun 20 '11 at 00:40
I've added an example. More examples are available at the documentation linked in the answer. — kba, Jun 20 '11 at 00:57

score 1 · Answer 2 · answered Jun 20 '11 at 00:27

1

How about considering using UNIX_TIMESTAMP? It uses the concept of elapsed time.

answered Jun 20 '11 at 00:27

Joyce

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it's prone to the 2038 date limit... ;) – Frankie Jun 20 '11 at 00:29
@Frankie 2038 is in the ... *future*~ – mauris Jun 20 '11 at 00:29
@thephpdeveloper have you seen any of those blockbuster's movies that destroy the world as we know it but keep your web-server running? There. I guess you can add a cron to 2037 to reset your date back to 1970... – Frankie Jun 20 '11 at 00:31
if programmers behave and use time_t type, instead of the uint32 type, we are safe! time_t is bound to get changed to a uint64 before the uint32 overflow... or so i hope – Vinicius Kamakura Jun 20 '11 at 00:35
@Frankie I know all the over flow stuff. just sayin' – mauris Jun 20 '11 at 00:38

score 1 · Answer 3 · answered Jun 20 '11 at 00:59

The "old" way to compare two or more dates is to convert then to an unix timestamp (seconds in float) using strtotime() function. For example:

if((strtotime('2011-05-10') - strtotime('2011-05-01')) > 604800)
{
    echo('A week has passed');
}

if((strtotime('2011-06-10') - strtotime('2011-05-01')) > 2629743)
{
    echo('A month has passed');
}

Or the "new" way is to use the DateTime class bundled with PHP 5.2 or newer. Have a look at http://php.net/manual/en/book.datetime.php.

score 0 · Answer 4 · answered Jun 20 '11 at 00:28

0

And of course date_diff has plenty of examples.

answered Jun 20 '11 at 00:28

Candide

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score 0 · Answer 5 · answered Jun 20 '11 at 00:29

You need to consider what you are exactly looking for.

Are you looking to filter dates older than a week? You can do that comparison on the SQL and you don't burden PHP with date comparisons.
Are you wanting a date difference? Again, I suggest putting it in SQL and just display the result.

score 0 · Answer 6 · answered Jun 20 '11 at 00:30

0

This will give you the number of seconds between the two dates:

<?php
$time = '2011-06-20';
$timeDiff = time() - strtotime($time);
echo $timeDiff;
?>

You could divide this value by 86,400 to get the number of days, and so on.

answered Jun 20 '11 at 00:30

Joel

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That can get tripped up by daylight saving changes, especially if you need more precision than "1 day". It is not recommended. – staticsan Jun 20 '11 at 00:33

PHP compare dates

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