<?php

public function getAll($sort) {
        if($sort == NULL){
            $sort = 'name';
        }
        echo $sort;
        $sql = 'SELECT name, second_name, group_number, summary
                FROM students ORDER BY :x';
        $stmt = $this->dbh->prepare($sql);
        $stmt->bindValue(':x', $sort);
        $stmt->execute();
        return $stmt->fetchAll(\PDO::FETCH_CLASS, 'app\models\Students');