public static function header($buffer=false) {
        global $CFG;
        ob_start();
?>
<style>
    .card {
    display: inline-block;
    padding: 0.5em;
    margin: 12px;
    border: 1px solid black;
    height: 9em;
    overflow-y: hidden;
}
 .card div {
    height: 8em;
    overflow-y: hidden;
    text-overflow: ellipsis;
}

#loader {
      position: fixed;
      left: 0px;
      top: 0px;
      width: 100%;
      height: 100%;
      background-color: white;
      margin: 0;
      z-index: 100;
}
</style>
<link rel="stylesheet" href="<?= $CFG->staticroot ?>/plugins/jquery.bxslider/jquery.bxslider.css" type="text/css"/>
<?php
        $ob_output = ob_get_contents();
        ob_end_clean();
        if ( $buffer ) return $ob_output;
        echo($ob_output);
    }