How do I generate a random time interval and add it to a mysql datetime using php?

I have many rows in mysql table with datetime's in the for开发者_开发知识库mat of:

2008-12-08 04:16:51 etc

I'd like to generate a random time interval of anywhere between 30 seconds, and 3 days and add them to the time above.

a) how do I generate a random time between 30 and 3 days?

b) how do I add this time to the date time format above?

I imagine i need to do a loop to pull out all the info, do the math in php, and then update the row...

Any ideas?

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Using MySQL's rand() function:

update [table] set [field] = now() + interval floor(rand()*(60*60*24*3)) second;

wil get you the current datetime + between 0 seconds and three days.

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easier way.

$new_date = date('Y-m-d h:i:s', strtotime('2008-12-08 04:16:51 +'.rand(30, 60 * 60 * 24 * 3).' seconds'));

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Would you be able to use a random unix timestamp and convert into the MySQL timestamp format? I would assume you could so something like:

$randomTime = time() + rand( 30, 86400 * 3 );   // since there are 86400 seconds in a day,
                                                        // this should generate a random time
                                                        // 3-30 days from now
$randomTimeString = date( "Y-m-d H:i:s", $randomTime ); // format the date (php.net/date)
$st = $mysqli->query( "...", $randomTimeString );       // insert it into the database
...

This probably isn't the most efficient solution, but it should work.