Assign checkbox array to variable

I am trying to use a checkbox to populate a single string in a database with specific formatting. I can successfully print the array, but I don't understand how to assign this to a variable in order to connect to the database and to use again elsewhere on the site. Here is the html:

 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="C">Commercials
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="CP">Commercial Print
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="V">Voice Overs
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="X">Background Work
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="F">Film
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="TV">Television
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="BT">Business Theatre Industrials
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="I">Film Industrials
 <input type="checkbox" id="bookCodes" name="bookCodes[]" value="MV">Music Videos

PHP:

foreach($_POST['bookCodes'] as $codes) {
    print "(".$codes.")";
};

I want the printed string to equal $bookCodes. I have tried putting the array in a function but then I get the first value only. Here is that code:

function prepBookCodes ($value)
{
    if (isset($_POST[$value])) {
        foreach ($_POST[$value] as $codes) {
            return "(" . $codes . ")";
        }
    }
}
$bookCodes = prepBookCodes('bookCodes');

print $bookCodes;

Any help would be greatly appreciated!