Comparisons show wrong result

[tflori]

Hello,

I encountered an issue with the following code:

Carbon::setToStringFormat('d.m.Y \a\t h:i a');
$dt = Carbon::parse('2022-05-03');
var_dump($dt->gt('2021-05-03'));

Carbon version: 2.55.2

PHP version: PHP 8.0.13

I expected to get:

bool(true)

But I actually get:

bool(false)

Ok, enough of your template. Let me explain. Someone in our company thought it works. And indeed it might work most of the time because noone is touching the to string format and php is smart enough to compare '2022-05-03' > '2021-05-03'. Also the documentation does not say it is save to use strings.

PHP itself also is very broken in this regard as the DateTime cannot be converted to string:

>>> $dt = new DateTime('2022-05-03')
=> DateTime @1651536000 {#189
     date: 2022-05-03 00:00:00.0 UTC (+00:00),
   }
>>> $dt > '2022-06-03'
=> true
>>> $dt > '2021-06-03'
=> true
>>> $dt < '2021-06-03'
=> false
>>> $dt < '2022-06-03'
=> false

The comparisons with strings seem to work more accendtially than anything else. Nevertheless the inline documetnations tells us it is working with strings (see: https://github.com/briannesbitt/Carbon/blob/2.55.2/src/Carbon/Traits/Comparison.php#L147). But that is only true if you don't change the toStringFormat.

My suggestion is to check if the given parameter in the comparison methods is a DateTime object and if not call ::resolveCarbon($date) or directly call ::resolveCarbon($date). Another option would be to throw but that's a breaking change.

Thanks!

[kylekatarnls]

Hello,

I agree. We should use resolveCarbon as we do with most of the methods. Here we want to get any string that parse() is able to handle and don't want to rely to setToStringFormat.

Meanwhile it get changed and released, I suggest to use instead:

$dt = Carbon::parse('2022-05-03');
var_dump($dt->gt(Carbon::parse('2021-05-03')));

Or simply:

var_dump($dt > Carbon::parse('2021-05-04'));