[Vlasenko Fedor]

switch ($_GET['profile']) {
    case 2:
        $style = 'style1.css';
        break;
    case 4:
        $style = 'style4.css';
        break;
    case 50:
        $style = 'style3.css';
        break;
    default:
        $style = 'style.css';
        break;
}

<link type="text/css" href="<?php echo $style;?>" rel="stylesheet" media="all">