Change date in field

[Bassman]

I have a date field in a table that I am trying to write a script that will extact the date and change it by one year, The field would contain a date like 2008-1-2 and I want to add one year to it so that it would be 2009-1-2 .
I have tried, without any luck, using the date("Y-m-d") function to change it. Is there a simple way to change it?
Thanks in advance.

[AfroJoJo]

<?php
echo date('Y')+1;
echo date('\-m\-d');
?>

[Bassman]

I got that far, but that takes todays date and adds a year to it and I want it to take a date that I have in a variable and increase it by a year? If I use,

echo date('Y',$mydate)+1;
echo date('\-m\-d',$mydate);

It returns 1970-12-31 every time where my variable equals 2007-1-2.

Thanks

[felgall]

$d = date('d',$mydate);
$m = date('m',$mydate);
$y = date('Y',$mydate);
echo date('Y-m-d',mktime(0,0,0,$m,$d,$y+1));

[Basil]

I've done a little test to see what would be the fastest way to do this. The quickest, and least accurate way to do it would be to simply add a year to the date.

365.25*24*60*60 = 31557600 (~seconds in a year)
So you could just do

echo date("Y-m-d",$mydate+31557600); 

This isn't 100% accurate, but it uses the least amount of processing, I don't know how accurate you need it to be.

The second way you can do this (quickly and accurately) is using the strtotime function. Something like this..

echo date("Y-m-d",strtotime("+1 year",$mydate)); 

This is around 2.5 times slower than the first method, but should be 100% accurate.

The third method is using mktime. This is about 3 times slower than the first method.

First you get the month, day and year from your time stamp, then you plug them into mktime, adding 1 to the year.

$d = explode("-",date("n-j-Y",$mydate));
echo date("Y-m-d",mktime(0,0,0,$d[0],$d[1],$d[2]+1)); 

This is the same as doing this..

echo date("Y-m-d",mktime(0,0,0,date("n",$mydate),date("j",$mydate),date("Y",$mydate)+1)); 

Except by using an array to hold the values php only has to process one date function instead of 3 inside of mktime, this makes it roughly twice as fast.