OOP數據庫連接/斷開類

Question

我剛剛開始學習面向對象編程的概念，並將一個用於連接數據庫，選擇數據庫和關閉數據庫連接的類組合在一起。 到目前為止，除了關閉與數據庫的連接外，一切似乎都沒問題。

    class Database {

    private $host, $username, $password;
    public function __construct($ihost, $iusername, $ipassword){
        $this->host = $ihost;
        $this->username = $iusername;
        $this->password = $ipassword;
    }
    public function connectdb(){
        mysql_connect($this->host, $this->username, $this->password)
            OR die("There was a problem connecting to the database.");
        echo 'successfully connected to database<br />';
    }
    public function select($database){
        mysql_select_db($database)
            OR die("There was a problem selecting the database.");
        echo 'successfully selected database<br />';
    }
    public function disconnectdb(){
        mysql_close($this->connectdb())
            OR die("There was a problem disconnecting from the database.");
    }
}

$database = new database('localhost', 'root', 'usbw');
$database->connectdb();
$database->select('msm');
$database->disconnectdb();

當我嘗試斷開與數據庫的連接時，我收到以下錯誤消息：

Warning: mysql_close(): supplied argument is not a valid MySQL-Link resource in F:\Programs\webserver\root\oop\oop.php on line 53

我猜這不像在mysql_close函數的括號中放置connectdb方法那么簡單，但找不到正確的方法。

謝謝

Answer 1

我會在你的類中添加一個連接/鏈接變量，並使用析構函數。 這也將使您不必忘記關閉連接，因為它會自動完成。
您需要傳遞給mysql_close（）的是$ this->鏈接。

class Database {

    private $link;
    private $host, $username, $password, $database;

    public function __construct($host, $username, $password, $database){
        $this->host        = $host;
        $this->username    = $username;
        $this->password    = $password;
        $this->database    = $database;

        $this->link = mysql_connect($this->host, $this->username, $this->password)
            OR die("There was a problem connecting to the database.");

        mysql_select_db($this->database, $this->link)
            OR die("There was a problem selecting the database.");

        return true;
    }

    public function query($query) {
        $result = mysql_query($query);
        if (!$result) die('Invalid query: ' . mysql_error());
        return $result;
    }

    public function __destruct() {
        mysql_close($this->link)
            OR die("There was a problem disconnecting from the database.");
    }

}

用法示例：

<?php
    $db = new Database("localhost", "username", "password", "testDatabase");

    $result = $db->query("SELECT * FROM students");

    while ($row = mysql_fetch_assoc($result)) {
        echo "First Name: " . $row['firstname'] ."<br />";
        echo "Last Name: "  . $row['lastname']  ."<br />";
        echo "Address: "    . $row['address']   ."<br />";
        echo "Age: "        . $row['age']       ."<br />";
        echo "<hr />";
    }
?>

編輯：
所以人們實際上可以使用這個類，我添加了缺少的屬性/方法。
下一步是擴展查詢方法，包括注入保護和任何其他幫助函數。
我做了以下更改：

• 添加了缺少的私有屬性
• 添加了__construct($host, $username, $password, $database)
• 將connectdb()和select()合並到__construct()節省額外的兩行代碼。
• 添加了query($query)
• 示例用法

如果我寫了一個錯字或錯誤，請留下建設性的評論，以便我可以為其他人解決。

編輯23/06/2018

正如所指出的那樣，mysql已經過時了，因為這個問題仍然定期訪問，我想我會發布一個更新的解決方案。

class Database {

    private $mysqli;
    private $host, $username, $password, $database;

    /**
     * Creates the mysql connection.
     * Kills the script on connection or database errors.
     * 
     * @param string $host
     * @param string $username
     * @param string $password
     * @param string $database
     * @return boolean
     */
    public function __construct($host, $username, $password, $database){
        $this->host        = $host;
        $this->username    = $username;
        $this->password    = $password;
        $this->database    = $database;

        $this->mysqli = new mysqli($this->host, $this->username, $this->password)
            OR die("There was a problem connecting to the database.");

        /* check connection */
        if (mysqli_connect_errno()) {
            printf("Connect failed: %s\n", mysqli_connect_error());
            exit();
        }

        $this->mysqli->select_db($this->database);

        if (mysqli_connect_errno()) {
            printf("Connect failed: %s\n", mysqli_connect_error());
            exit();
        }

        return true;
    }

    /**
     * Prints the currently selected database.
     */
    public function print_database_name()
    {
        /* return name of current default database */
        if ($result = $this->mysqli->query("SELECT DATABASE()")) {
            $row = $result->fetch_row();
            printf("Selected database is %s.\n", $row[0]);
            $result->close();
        }
    }

    /**
     * On error returns an array with the error code.
     * On success returns an array with multiple mysql data.
     * 
     * @param string $query
     * @return array
     */
    public function query($query) {
        /* array returned, includes a success boolean */
        $return = array();

        if(!$result = $this->mysqli->query($query))
        {
            $return['success'] = false;
            $return['error'] = $this->mysqli->error;

            return $return;
        }

        $return['success'] = true;
        $return['affected_rows'] = $this->mysqli->affected_rows;
        $return['insert_id'] = $this->mysqli->insert_id;

        if(0 == $this->mysqli->insert_id)
        {
            $return['count'] = $result->num_rows;
            $return['rows'] = array();
            /* fetch associative array */
            while ($row = $result->fetch_assoc()) {
                $return['rows'][] = $row;
            }

            /* free result set */
            $result->close();
        }

        return $return;
    }

    /**
     * Automatically closes the mysql connection
     * at the end of the program.
     */
    public function __destruct() {
        $this->mysqli->close()
            OR die("There was a problem disconnecting from the database.");
    }
}

用法示例：

<?php
    $db = new Database("localhost", "username", "password", "testDatabase");

    $result = $db->query("SELECT * FROM students");

    if(true == $result['success'])
    {
        echo "Number of rows: " . $result['count'] ."<br />";
        foreach($result['rows'] as $row)
        {
            echo "First Name: " . $row['firstname'] ."<br />";
            echo "Last Name: "  . $row['lastname']  ."<br />";
            echo "Address: "    . $row['address']   ."<br />";
            echo "Age: "        . $row['age']       ."<br />";
            echo "<hr />";
        }
    }

    if(false == $result['success'])
    {
        echo "An error has occurred: " . $result['error'] ."<br />";
    }
?>

Answer 2

你沒有從connectdb()返回任何東西但是你正在傳遞這個函數返回mysql_close() 。

Answer 3

你應該知道在PHP 4中引入了mysql_*函數，這些函數已經超過了你的1。 此API非常陳舊，並且該過程已開始實際棄用此擴展 。

您不應該在2012年使用mysql_*函數編寫新代碼。

有兩個非常好的選擇： PDO和MySQLi 。 兩者都已經考慮了面向對象的代碼，並且它們還使您能夠使用預准備語句 。

您在使用PDO編寫的原始帖子中顯示的示例如下所示：

//connect to the the database
$connection = new PDO('mysql:host=localhost;dbname=msm', 'username', 'password');
//disconnects
$connection = null;

當然，有更復雜的用例，但有時間要進化。

Answer 4

mysql_close需要一個參數來斷開連接但你什么也沒提供。

class Database {

    private $host, $username, $password, $con;

    public function __construct($ihost, $iusername, $ipassword){
        $this->host = $ihost;
        $this->username = $iusername;
        $this->password = $ipassword;
        $this->con = false;
    }


    public function connect() {
        $connect = mysql_connect($this->host, $this->username, $this->password);
        return $connect;
    }


    public function connectdb(){
        $conn = $this->connect();
        if($conn)
        {
            $this->con = true;
            echo "Successsfully Connected. 
";
            return true;
        }
        else {
            echo "Sorry Could Not Connect. 
";
            return false;
        }
    }


    public function select($database){
        if($this->con)
        {
            if(mysql_select_db($database))
            {
                echo "Successfully Connected Database. $database. 
";
                return true;
            }
            else
            {
                echo "Unknown database. 
";
            }
        }
        else {
            echo "No active Connection. 
";
            return false;
        }
    }


    public function disconnectdb(){
        if($this->con)
        {
            if(mysql_close($this->connect()))
            {
                $this->con = false;
                echo "Successfully disconnected. 
";
                return true;
            }
        }
        else
        {
            echo "Could Not disconnect. 
";
            return false;
        }
    }

}

    $database = new database('localhost', 'root', '');
    $database->connectdb();
    $database->select('databaseoffacebook');
    $database->disconnectdb();

Answer 5

面向對象編程與PDO和mysqli配合得很好。 試試看

Answer 6

<?php

class Database{

    private $link;
    //private $host,$username,$password,$database;
    //private $status;

    public function __construct(){

        $this->host         =   'localhost';
        $this->username     =   'root';
        $this->password     =   '';
        $this->database     =   'workclass';

        $this->link = mysqli_connect($this->host,$this->username,$this->password);

        $this->status = mysqli_select_db($this->link,$this->database);

        if (!$this->status) {
            return $this->status="Failed to Connected with Database";
        }else{
            return $this->status="Database is connected";
        }
    }
}

$object = new Database();

echo $object->status;

?>