php - Laravel regex validation for price OR empty

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I am trying to make a regex
for price OR empty.
I have the price part (Dutch uses comma instead of point)
which actualy
works

/^\d+(,\d{1,2})?$/

The
regex above validates ok on the value 21,99

Now
I try to add the empty part so the field can be... just empty
^$

/(^$|^\d+(,\d{1,2})?$)/

But
Laravel starts to complain as soon as I change the regex:
"Method
[validate^\d+(,\d{1,2})?$)/] does not
exist."

Works
ok:

$rules =
            [

 'price' =>
            'regex:/^\d+(,\d{1,2})?$/'
];

Laravel
says no...:

$rules = [

            'price' =>
            'regex:/(^$|^\d+(,\d{1,2})?$)/'
];

Kenken9990
answer - Laravel doesn't break anymore but an empty value is still
wrong:

$rules = [

            'price' =>
            'regex:/^(\d+(,\d{1,2})?)?$/'
];

Answer

is this work
?

$rules = [

            'price' =>
            'nullable|regex:/^(\d+(,\d{1,2})?)?$/'
];