how to get checkbox value from database in php for update data?

in database values are stored as "A,B,C,D,E,F" etc. now i have to fetch those data in the form for update. i have to check the checkbox if it matches the value with database value.

i am doing this kind of code(which i know is wrong)

    <input type="checkbox" name="time[]" value="free" <?php if(!strpos($row['best'], 'free')=="false") { echo "checked='checked'";} ?> />Free
    <input type="checkbox" name="time[]" value="Open" <?php if(!strpos($row['best'], 'Open')=="false") { echo "checked='checked'"; }?>/>Open Source
    <input type="checkbox" name="time[]" value="portable" <?php if(!strpos($row['best'], 'portable')=="false") { echo "checked='checked'"; }  ?> />Portable
    <input type="checkbox" name="time[]" value="support" <?php if(!strpos($row['best'], 'support')=="false") {
                        echo "checked='checked'"; }?> />Support