<input type='checkbox' value='1C-Q1-5' name='answer1[]' class='radio'>

$_POST['answer1'] //this is an array

$answers = $_POST['answer1']
// we pass the fetched data first
// then we transform then into a string if you want to save them in your database

$final_answers = implode("," , $answers);

//the $final_answers variable is a STRING that now holds all the chosen checkboxes but are separated by a comma
//for example, it will hold a value "1C-Q1-5, 1C-Q1-2, 1C-Q1-1", if the user has checked the 1st, 2nd and 5th checkboxes