too long

I am having trouble to figure out how to process the checkbox values that were selected in Angular Forms and add those selected values to the mySql DB.

For example, lets say I have these checkboxes in the Angular JS Form:

Value1: <input type="checkbox" ng-model="formData.checkbox.value1"> <br/>
Value2: <input type="checkbox" ng-model="formData.checkbox.value2"> <br/>
Value3: <input type="checkbox" ng-model="formData.checkbox.value3"> <br/>

When the above formData is sent to submit.php using $http.post like this:

        $http({
        method  : 'POST',
        url     : 'submit.php',
        data    : $.param($scope.formData),  // pass in data as strings
        headers : { 'Content-Type': 'application/x-www-form-urlencoded' }  // set the headers so angular passing info as form data (not request payload)
    })

how can I process these checked values from php side?

My questions are:

1) How are the checkbox values passed over the php? Does Angular only send an array of checkbox values that were selected like: checkbox[0], checkbox[2], etc.. to php (or) or does it send all checkbox statuses as True or False in an array like

$checkbox[value1] = true;
$checkbox[value2] = false;
$checkbox[value3] = true;

?

2) How to process these checkboxes and only add selected checbboxes to sql? I have created a checkbox column (string type) in my MySql and when I try to insert $_POST['checkbox'] into this column, I am receiving a Array to string conversion error. I also tried converting this array to string using implode which doesnt work neither. I am basically trying to store the value of the checked checkboxes (using the model name) in DB so when retrieved later we can tell which checkbox was checked and which wasnt. So can someone give an example of how checkbox values are passed in php that is then stored into DB?

Usually in php based site, I add the checkbox value= to the form and then insert the list of checkbox values (converted to string) to DB since php only posts values of selected checkboxes. But I am not sure how this is done if Angular is used client side and php is only used in the server side. Any help will be great please!