PHP PDO操作mysql不注意的话依然存在SQL注入

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我们先来看一段代码

dbh = new PDO("mysql:host=localhost; dbname=demo", "user", "pass");
$dbh->exec("set names 'gbk'");
$sql="select * from test where name = ? and password = ?";
$stmt = $dbh->prepare($sql);
$exeres = $stmt->execute(array($name, $pass));

上面这段代码虽然使用了pdo的prepare方式来处理sql查询，但是当PHP版本
dbh = new PDO("mysql:host=localhost; dbname=demo", "user", "pass");
$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false); 
$dbh->exec("set names 'utf8'");
$sql="select * from test where name = ? and password = ?";
$stmt = $dbh->prepare($sql);
$exeres = $stmt->execute(array($name, $pass));

<?php 
dbh = new PDO("mysql:host=localhost; dbname=demo", "user", "pass");
$dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, false); 
$dbh->exec("set names &#39;utf8&#39;");
$sql="select * from test where name = ? and password = ?";
$stmt = $dbh->prepare($sql);
$exeres = $stmt->execute(array($name, $pass));