<?php
$pdo->query("create table users (id int, name varchar(100))");
$pdo->query("insert into users (id,name) values (1,'Bobby Tables')");
echo $pdo->query("select name from users")->fetchColumn(),"\n";
$id = "id;drop table users";
$stmt = $pdo->prepare("select name from users where id=?");
$stmt->execute([$id]);
$id = mysqli_real_escape_string($mysqli, $id);
$stmt = $pdo->query("select name from users where id=$id");
echo $pdo->query("select name from users")->fetchColumn(),"\n";