php - mysqli_stmt::bind_result():绑定(bind)变量的数量与准备好的语句中的字段数量不匹配(一个函数工作，另一个不工作)

Question

这个问题以前有人回答过，但格式不一样。

我正在尝试创建一个对象方法来获取数据库行。我不断收到标题错误。奇怪的是，如果我直接在父类方法中调用函数的相同代码，它就可以工作。这是两个例子。

示例 1:作品从单独的 PHP 页面调用的函数，例如: $email = trim($_POST['email']); $password = trim($_POST['密码']);

$found_user = User::authenticate($email, $password);

这是正在运行的函数。 (如果我正在制作一个可重用的函数来测试我的代码是否错误，我会设置该函数)

public static function authenticate($username="", $password="") {

    $db = Database::getInstance();
    $mysqli = $db->getConnection();

    $field = 'email';

    $sql_query  = "SELECT * ";
    $sql_query .= "FROM `".static::$table_name."`";
    $sql_query .= "WHERE {$field}=? ";
    $sql_query .= "LIMIT 1";

    $stmt = $mysqli->stmt_init();

    if (!$stmt->prepare($sql_query)) {
        $error = "Errormessage: " . $mysqli->error;
        return $error;
    }

    if (!$stmt->prepare($sql_query)) {
        $error = "Errormessage: " . $stmt->error;
        return $error;
    } else {
        $stmt->prepare($sql_query);

        $valueType = gettype($username);

        if ($valueType == 'string') {
            $stmt->bind_param('s', $username);  
        } else if ($valueType == 'integer') {
            $stmt->bind_param('i', $username);  
        } else if ($valueType == 'double') {
            $stmt->bind_param('d', $username);  
        } else {
            $stmt->bind_param('b', $username);  
        }

        $stmt->execute();
        $result = $stmt->get_result();

        return $result->fetch_object();
    }       
}

现在，如果我在相同的方法中调用该函数，但来自扩展类(父类是扩展了 DatabaseOptions 的 User)。函数是这样写的:

public static function authenticate($username="", $password="") {
    $dbObject = static::get_row('email', $username);

    if (isset($dbObject)) {
        return $dbObject;
    }
}

DatabaseObject 中的函数:

public function get_row($field, $value) {
    $db = Database::getInstance();
    $mysqli = $db->getConnection();

    $sql_query  = "SELECT * ";
    $sql_query .= "FROM `".static::$table_name."`";
    $sql_query .= "WHERE {$field}=? ";
    $sql_query .= "LIMIT 1";

    $stmt = $mysqli->stmt_init();

    if (!$stmt->prepare($sql_query)) {
        $error = "Errormessage: " . $stmt->error;
        return $error;
    } else {
        $stmt->prepare($sql_query);

        $valueType = gettype($value);

        if ($valueType == 'string') {
            $stmt->bind_param('s', $value); 
        } else if ($valueType == 'integer') {
            $stmt->bind_param('i', $value); 
        } else if ($valueType == 'double') {
            $stmt->bind_param('d', $value); 
        } else {
            $stmt->bind_param('b', $value); 
        }

        $stmt->execute();
        $result = $stmt->get_result();

        return $result->fetch_object();
    }           
}

Answer 1

public function get_row($field, $value) {
    $db = Database::getInstance();
    $mysqli = $db->getConnection();

    $sql_query  = "SELECT * ";
    $sql_query .= "FROM `".static::$table_name."`";
    $sql_query .= "WHERE {$field}=? ";
    $sql_query .= "LIMIT 1";

    if ($stmt = $mysqli->prepare($sql_query)) {
        $valueType = gettype($value);

        if ($valueType == 'string') {
            $stmt->bind_param('s', $value); 
        } else if ($valueType == 'integer') {
            $stmt->bind_param('i', $value); 
        } else if ($valueType == 'double') {
            $stmt->bind_param('d', $value); 
        } else {
            $stmt->bind_param('b', $value); 
        }

        $stmt->execute();
        $result = $stmt->get_result();
        return $result->fetch_object();
    } else {
        $error = "Errormessage: " . $stmt->error;
        return $error;
    }           
}

原始代码的问题在于我使用的是 bind_result($row)，我从数据库中提取的行有多个需要绑定(bind)的值。如$result = $stmt->get_result 然后返回一个fetch_object();。