Passing a null DateTime to php function

Question

I have a function in php that I want to accept either a DateTime object or null. E.g.

function foo(DateTime $aDate){
   if ($aDate == null){
       echo "You passed a null variable";
   } else {
       echo "You passed the date " . $aDate->format('Y-m-d');
   }
}

Trouble is, because the function expects a DateTime object it flips out when I pass null to it and gives an error:

Catchable fatal error: Argument 1 passed to foo() must be an instance of DateTime, null given,...

How can I pass null to the function and avoid this error?

pcmoreno · Accepted Answer · 2018-08-08 12:57:08Z

7

add a ? to the type hint.

    function foo(?DateTime $aDate){
        if ($aDate == null){
            echo "You passed a null variable";
        } else {
            echo "You passed the date " . $aDate->format('Y-m-d');
        }
    }

This way only an explicit NULL or DateTime are allowed.

answered Aug 8, 2018 at 12:57

pcmoreno

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2 Comments

Adrian Wiik Over a year ago

Note that this is only possible in PHP >= 7.1.

Adrian Wiik Over a year ago

I was just too late to edit: The file where the function is called from must have declare(strict_types = 1); as its first statement, or it won't be enforced.

Community · Accepted Answer · 2017-05-23 10:32:31Z

6

Change from this:

function foo(DateTime $aDate){

To this:

function foo($aDate){

But if you still want to make sure the object passed is a DateTime object you can do this:

function foo(DateTime $aDate = null){

See here for more examples of Type Hinting.

edited May 23, 2017 at 10:32

CommunityBot

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answered Jul 31, 2013 at 14:55

Naftali

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5 Comments

Jason McCreary Over a year ago

Interesting that it doesn't allow null with type hinting. Part of me feels it should.

harryg Over a year ago

OK so what is the point in putting DateTime in the paramater list of the function if you can still pass a DateTime without it?

Naftali Over a year ago

@JasonMcCreary Ahh found the solution!

harryg Over a year ago

Yeah, the update makes more sense. I would like to force passing either a DateTime or null.

Adrian Wiik Over a year ago

This is possible in PHP 7.1 and above, see @pcmoreno's answer. IMO, his answer should be the accepted one now.

kwolfe · Accepted Answer · 2013-07-31 14:57:53Z

3

Make $aDate optional.

function foo(DateTime $aDate = null) {
    if($aDate) {
        //parse date
    } else {
        //null given
    }
}

answered Jul 31, 2013 at 14:57

kwolfe

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Comments

vascowhite · Accepted Answer · 2013-07-31 14:58:04Z

1

The way to do it is to assign a default value in the function declaration:-

function foo(DateTime $aDate = null){
   if (!$aDate){
       echo "You passed a null variable";
   } else {
       echo "You passed the date " . $aDate->format('Y-m-d');
   }
}

answered Jul 31, 2013 at 14:58

vascowhite

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