我是mysql的新手。这是我的代码块：

public function updateTable($obj, $column_names, $table_name, $bannerid) {

    $c = (array) $obj;
    $id = $bannerid;
    $keys = array_keys($c);
    $columns = '';
    $values = '';
    foreach($column_names as $desired_key){ // Check the obj received. If blank insert blank into the array.
       if(!in_array($desired_key, $keys)) {
            $$desired_key = '';
        }else{
            $$desired_key = $c[$desired_key];
        }
        $columns = $columns.$desired_key.',';
        $values = $values."'".$$desired_key."',";
    }
    //$query = "INSERT INTO ".$table_name."(".trim($columns,',').") VALUES(".trim($values,',').")";
    //mysql_query("UPDATE blogEntry SET content = '$udcontent', title = '$udtitle' WHERE id = $id");
    $query = "UPDATE ".$table_name." SET "."(".trim($columns,',').") = VALUES(".trim($values,',').")" ."WHERE id = '$id'" ;
    $r = $this->conn->query($query) or die($this->conn->error.__LINE__);

    if ($r) {
        $new_row_id_update = $this->conn->insert_id;
        return $new_row_id_update;
        } else {
        return NULL;
    }
}

下面是我得到的错误：
sql语法有错误；请查看与您的mysql服务器版本对应的手册，以了解使用near'（image\u url，intro）=values（'800bf5f59a1d13c8.jpg'，'，sd，cfcjaklewfh ewiuofejkfdh'的正确语法，该语法位于第1100行