在php中插入sql語句錯誤：未選擇數據庫

Question

所以我正在嘗試制作一份注冊表。 我創建了一個php MySQL類，它使用構造函數為我的addElement函數建立與新的MySQLi（）for verifyLogin函數和mysql_connect（）的連接。

錯誤是我的addElement函數，SQL語句正確寫出但它似乎沒有連接到數據庫。 我已經檢查過所有的名字都是正確的。 有任何想法嗎？

<?php

class MySQL {

private $connection;
private $conn;
private $databaseName;

function __construct($dbServer, $dbUser, $dbPassword, $dbName) {
    $this->connection = new MySQLi($dbServer, $dbUser, $dbPassword, $dbName)
        or die('PROBLEM CONNECTING TO DATABASE');

    $this->conn = mysql_connect($dbServer, $dbUser, $dbPassword);
        echo $this->conn;

    $databaseName = $dbName;
}

function verifyLogin($table, $email, $password) {

    $query = "SELECT *
            FROM ?
            WHERE email = ?
            AND password = ?
            LIMIT 1";

    if($statement = $this->connection->prepare($query)) {
        $statement->bind_param('sss', $table, $email, $password);
        $statement->execute();

        if($statement->fetch()) {
            $statement->close();
            return true;    
        }
        else {
            return false;
        }
    }

}

function addElement($table, $firstName, $lastName, $email, $mobile, $password,
                        $faculty, $campus) {


    $query = "INSERT INTO $table (first_name, last_name, email, mobile, password, faculty, campus_location) 
            VALUES('$firstName', '$lastName','$email','$mobile',
            '$password','$faculty','$campus');";
    echo $query;

    mysql_select_db($this->databaseName, $this->conn);

    if(!mysql_query($query)) {
        die('Error: ' . mysql_error()); 
    }

    mysql_close($this->connection);
}


}

?>

Answer 1

要在MySQLi中選擇數據庫，您需要選擇它，如下所示：

$db = new mysqli("localhost", "my_user", "my_password", "database_name");

要么

$db = new mysqli("localhost", "my_user", "my_password");
$db->select_db('database_name');

而不是MySQL：

$db = mysql_connect('localhost', 'my_user', 'my_password');
$db_selected = mysql_select_db('database_name', $db);

MySQLi： http ：//www.php.net/manual/en/mysqli.select-db.php

MySQL： http ： //www.php.net/manual/en/function.mysql-select-db.php

Answer 2

你正在混合mysql和mysqli php驅動程序。

由於不推薦使用mysql驅動程序，我建議使用mysqli。

PHP文檔： http ： //www.php.net/manual/en/book.mysqli.php

開始的好概述： http ： //www.dreamincode.net/forums/topic/54239-introduction-to-mysqli-and-prepared-statements/