如何从 php 获取 sql 中受影响的行

我写下了以下代码。但是当我尝试获取受影响的行（以检查用户详细信息是否与数据库的详细信息匹配）时，即使语句成功执行，它也始终返回 0 作为受影响的行。我做错了什么？

if($connection){
$username = "admin";
$password = "admin";
$statement = mysqli_prepare($connection,"SELECT * FROM  `admin` WHERE username = ? AND password = ?");
mysqli_stmt_bind_param($statement,"ss",$username,$password);
mysqli_stmt_execute($statement);
if(mysqli_affected_rows($connection) == 1){
    $response = array('response'=>true);
}else{
    $response = array('response'=>false);
}
echo json_encode($response);
mysqli_stmt_close($statement);
mysqli_close($connection);     }