Flutter : checkbox sent array data to POST json body parameter - arrays

Question

I have problem with checkbox to add parameter hit to POST data for API.
This is POST data sent when I clicked Save Button :
Map<String, String> params = {
'breed_id': selectedBreedID!,
'gender': _selectedGender!,
'weight': weightTxtCtrl.text,
'date_of_birth': _dateController.text,
pHfirst! : pHlast!
};
final response = await http.post(
Uri.parse(
"http://localhost:8000/api/v1/pet",
),
headers: {'Authorization': 'Bearer $token'},
body: params,
);
}
this is my checkbox code :
String? pHfirst = "";
String? pHlast = "";
List<PetHealthModel> petHealths = [];
List<PetHealthModel>customPets=[];
petHealths.isNotEmpty
? Padding(
padding: const EdgeInsets.all(8.0),
child: Column(
children: petHealths.map((e) {
var healthsID = customPets.map((e) => e.id).toList();
return CheckboxListTile(
title: Text(e.healthStatus),
value: healthsID.contains(e.id),
onChanged: (bool? value) {
if (value == true) {
setState ((){
customPets.add(e);
for (var element in customPets) {
pHfirst = "pet_healths["+element.id.toString()+"]";
pHlast = ""+element.id.toString()+",";
log(pHfirst!+" : "+pHlast!);
}
});
} else {
setState((){
customPets.remove(e);
for (var element in customPets) {
pHfirst = "pet_healths["+element.id.toString()+"]";
pHlast = ""+element.id.toString()+",";
log(pHfirst!+" : "+pHlast!);
}
});
}
}
);
}).toList(),
),
),
Here's the log that printed :
sample if select 3, 4, 5
sample if select 2 only
From the sample below is I know that my code works, but when I called it in Map<String, String> params it only called the last pet_healths that I selected not print all of that :
This is the result that in debut we can see that 5 data printed, but when it called to Map<String, String> Param it only 1 last data