<?php

$db = new PDO("mysql:host=$host;dbname=$db_name", $user, $pass);

$res = $db->prepare("INSERT INTO students (first_name, last_name, student_id, phone) VALUES (:first_name, :last_name, :student_id, :phone)");

$n = intval(trim(fgets(STDIN)));

for ($i = 0; $i < $n; $i++) {
    try {
        $input = explode(" ", trim(fgets(STDIN)));

        $first_name = $input[0];
        $last_name = $input[1];
        $student_id = $input[2];
        $phone = null;

        if ($first_name == '') {
            throw new PDOException("First Name cannot be empty!");
        }
        elseif (preg_match('~[0-9]~', $first_name)) {
            throw new PDOException("First Name must contain only letters!");
        }
        elseif ($last_name == '') {
            throw new PDOException("Last Name cannot be empty!");
        }
        elseif (preg_match('~[0-9]~', $last_name)) {
            throw new PDOException("Last Name must contain only letters!");
        }
        elseif (!is_numeric($student_id)) {
            throw new PDOException("Invalid Student ID");
        }

        $res->execute([':first_name' => $first_name, 'last_name' => $last_name, 'student_id' => $student_id, 'phone' => $phone]);

        $res = null;
        $db = null;
    }
    catch (PDOException $e) {
        echo $e->getMessage();
    }
}