Render HTML checkbox inputs based on MySQL data

Assuming $row is an associative array mapping column name onto a boolean 1 or 0 value, you could do something like this:

foreach($row as $colname=>$boolean)
{
    //create a name for the checkbox which will produce a nice 
    //PHP array of checked column names in $_POST['col']
    $name="col[$colname]";

    //create an id for the checkbox
    $id='col'.$colname;

    //now we output the checkbox - on form submission you will
    //see an element in $_POST['col'][$colname] if checked, and
    //no element at all if unchecked...
    echo '<input type="checkbox" value="1" '.
       'name="'.$name.'" id="'.$id.'" '.
       ($boolean?'checked="checked"':'').
       '>';

    //output a label - note we'd tied this to the id of the checkbox
    //which means you can click the label to tick the box   
    echo "<label for=\"$id\">colname</label><br/>";
}

When the form is submitted, you'll get an array in $_POST['col'] indexed by column name, but only for those boxes which are checked, so you'd set to false any columns which are not set.

See here: http://dev.w3.org/html5/spec/Overview.html#checkbox-state

So, try this:

<input type="checkbox" checked="true">