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?

score 7 · Answer 1 · answered Aug 08 '18 at 12:57

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 08 '18 at 12:57

pcmoreno

101
2
5

Note that this is only possible in PHP >= 7.1. – Adrian Wiik Jul 10 '20 at 15:26
1

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. – Adrian Wiik Jul 10 '20 at 15:33

score 6 · Accepted Answer · edited May 23 '17 at 10:32

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 '17 at 10:32

Community

1
1

answered Jul 31 '13 at 14:55

Naftali

144,921
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303

1

Interesting that it doesn't allow `null` with type hinting. Part of me feels it should. – Jason McCreary Jul 31 '13 at 14:57
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? – harryg Jul 31 '13 at 14:57
@JasonMcCreary Ahh found the solution! – Naftali Jul 31 '13 at 14:57
Yeah, the update makes more sense. I would like to force passing either a `DateTime` or `null`. – harryg Jul 31 '13 at 15:00
1

This is possible in PHP 7.1 and above, see @pcmoreno's answer. IMO, his answer should be the accepted one now. – Adrian Wiik Jul 10 '20 at 15:28

score 3 · Answer 3 · answered Jul 31 '13 at 14:57

3

Make $aDate optional.

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

answered Jul 31 '13 at 14:57

kwolfe

1,663
3
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score 1 · Answer 4 · answered Jul 31 '13 at 14:58

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');
   }
}

Passing a null DateTime to php function

4 Answers4