I just noticed a typo in one line:
PHP Code:
    $content .= '<div id="' str_replace('_''-'$box_id 'Content') . '" class="sideBoxContent">'
The closing ) is misplaced.
PHP Code:
    $content .= '<div id="' str_replace('_''-'$box_id) . 'Content" class="sideBoxContent">'