Question

我刚刚开始学习面向对象编程的概念，并且已经组合了一个用于连接数据库，选择数据库和关闭数据库连接的类。到目前为止，除了关闭与数据库的连接外，一切似乎都没问题。

    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();

当我尝试断开与数据库的连接时，收到以下错误消息：

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

我猜测它并不像将connectdb方法放在mysql_close函数的括号中那么简单，但无法找到正确的方法。

由于

Answer 1

我会在你的类中添加一个连接/链接变量，并使用析构函数。这也将使您不必记住关闭连接，因为它会自动完成您需要将$ this-＆gt;链接传递给mysql_close（）。

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.");
    }

}

示例用法：

<?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 />";
    }
?>

编辑：
所以人们实际上可以使用这个类，我添加了缺少的属性/方法下一步是扩展查询方法，包括注入保护和任何其他帮助函数我做了以下更改：

添加了缺少的私有属性
已添加__construct($host, $username, $password, $database)
将connectdb()和select()合并到__construct()中，可以节省额外的两行代码。
已添加query($query)
使用示例

如果我输入错字或错误，请留下建设性意见，以便我可以为其他人解决。

编辑23/06/2018

正如所指出的那样，mysql已经过时了，因为这个问题仍然定期访问，我想我会发布一个更新的解决方案。

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.");
    }
}

使用示例：

<?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

你没有从connectdb()返回任何内容，但是你已经将此函数返回mysql_close()。

Answer 3

你应该知道在PHP 4中引入了mysql_*函数，这些函数已经超过了你的1。这个API非常陈旧，而且这个过程实际上已经开始deprecating this extension。

您不应该在2012年使用mysql_*函数编写新代码。

有两个非常好的选择：PDO和MySQLi。两者都已经考虑了面向对象的代码，并且它们还使您能够使用prepared statements。

您在用PDO编写的原始帖子中显示的示例如下所示：

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

当然，还有更复杂的用例，但需要进一步发展。

Answer 4

mysql_close需要一个参数来断开连接，但你什么也没提供。


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

面向对象编程与PDO和mysqli配合得很好。试一试

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;

?>

OOP数据库连接/断开类

6 个答案: