How to get mysql database table fields in PHP

<?php
classShowTalbeColunms {
public static function showColunms($pdo,$colunmsName) {//判断传来的$pdo是否为pdo对象的实例化$b=is_a($pdo,&#39;PDO&#39;);
            if(!$b) {
                echo&#39;传来的对象不是PDO的实例化&#39;;
                exit();
            }
            $count = $pdo->query("SHOW FULL COLUMNS FROM ".$colunmsName);
            $arr=array();
            //如果查询到结果if($count) {
                $arr=$count->fetchAll();
                $colunms=array();
                for ($i=0; $i < count($arr); $i++) {
                    $colunms[$i]=$arr[$i][&#39;Field&#39;];
                }
            }
            //打印echo"<pre class="brush:php;toolbar:false">";
            print_r($colunms);
            echo"