<?php

// Достал студента из БД по паролю
$student = $db->isPswrdInDB($password);

// код обработки запроса сверху:
 public function isPswrdInDB($password)
    {
        $sql         = "SELECT * FROM students WHERE password= :password";
        $cpswrd      = $this->db->prepare($sql);
        $cpswrd->bindValue(':password', $password);
        $cpswrd->execute();
        $student = $cpswrd->fetchAll(PDO::FETCH_CLASS | PDO::FETCH_PROPS_LATE, "student");
        if (count($cpswrd) > 0) {
            return $student;
        } else
            return false;

    }