Compare given date with today

I have following

$var = "2010-01-21 00:00:00.0"

I'd like to compare this date against today's date (i.e. I'd like to know if this $var is before today or equals today or not)

What function would I need to use?

strtotime($var);

Turns it into a time value

time() - strtotime($var);

Gives you the seconds since $var

if((time()-(60*60*24)) < strtotime($var))

Will check if $var has been within the last day.

That format is perfectly appropriate for a standard string comparison e.g.

if ($date1 > $date2){
  //Action
}

To get today's date in that format, simply use: date("Y-m-d H:i:s").

So:

$today = date("Y-m-d H:i:s");
$date = "2010-01-21 00:00:00";

if ($date < $today) {}

That's the beauty of that format: it orders nicely. Of course, that may be less efficient, depending on your exact circumstances, but it might also be a whole lot more convenient and lead to more maintainable code - we'd need to know more to truly make that judgement call.

For the correct timezone, you can use, for example,

date_default_timezone_set('America/New_York');

Click here to refer to the available PHP Timezones.

Here you go:

function isToday($time) // midnight second
{
    return (strtotime($time) === strtotime('today'));
}

isToday('2010-01-22 00:00:00.0'); // true

Also, some more helper functions:

function isPast($time)
{
    return (strtotime($time) < time());
}

function isFuture($time)
{
    return (strtotime($time) > time());
}

You can use the DateTime class:

$past   = new DateTime("2010-01-01 00:00:00");
$now    = new DateTime();
$future = new DateTime("2021-01-01 00:00:00");

Comparison operators work*:

var_dump($past   < $now);         // bool(true)
var_dump($future < $now);         // bool(false)

var_dump($now == $past);          // bool(false)
var_dump($now == new DateTime()); // bool(true)
var_dump($now == $future);        // bool(false)

var_dump($past   > $now);         // bool(false)
var_dump($future > $now);         // bool(true)

It is also possible to grab the timestamp values from DateTime objects and compare them:

var_dump($past  ->getTimestamp());                        // int(1262286000)
var_dump($now   ->getTimestamp());                        // int(1431686228)
var_dump($future->getTimestamp());                        // int(1577818800)
var_dump($past  ->getTimestamp() < $now->getTimestamp()); // bool(true)
var_dump($future->getTimestamp() > $now->getTimestamp()); // bool(true)

^{* Note that === returns false when comparing two different DateTime objects even when they represent the same date.}

To complete BoBby Jack, the use of DateTime OBject, if you have php 5.2.2+ :

if(new DateTime() > new DateTime($var)){
    // $var is before today so use it

}