如何检查用户是否存在于 MySQL 数据库中？

Question

如何检查数据库中是否已经存在用户？

我有变量$name = $user_profile['name'];它成功返回用户名。

这是我检查用户是否已存在于数据库中的代码部分。

$user_profile = $facebook->api('/me');
$name = $user_profile['name'];
$mysqli = new mysqli("asd", "asdf", "pw", "asdssst");
/* Create the prepared statement */
$stmt = $mysqli->prepare("SELECT COUNT(*) AS num FROM myTable WHERE userName = ?") or die("Prepared Statement Error: %s\n" . $mysqli->error);
/* Bind results to variables */
$stmt->bind_param('s', $name);
/* Execute the prepared Statement */
$stmt->execute();
$data = $stmt->fetch();
if ($data['num'] > 0) {
    echo "bad";
    print "user already exists\n";
} else {
    echo "good";
    $apiResponse = $facebook->api('/me/feed', 'POST', $post_data);
    print "No user in database\n";
}
/* Close the statement */
$stmt->close();

无论用户是否在数据库中，它总是返回：good No user in database。这意味着$data['num'] 始终是0。

附：我知道我需要使用 FB 用户 ID 而不是用户名，但在这种情况下我需要这样做。

Answer 1

检查变量是否有结果。这样的事情应该可以工作。

//So you have your variable $name here + it returns a value
$name = $user_profile['name'];
//You can put this if statement anywhere below it
if($name > 1){
//log user in
}

Answer 2

我会用这样的东西

$mysqli = new mysqli('',"","","");
$query = 'SELECT username FROM user WHERE username = ?';
$stmt = $mysqli->prepare($query);
$name = 'asdf';
$stmt->bind_param('s', $name);
$stmt->execute();
$stmt->bind_result($user);
if($stmt->fetch())
   echo 'Username '.$user. ' exists';
else 
  echo 'User doesnt exists';
$stmt->close();