我剛剛開始學(xué)習(xí)面向?qū)ο缶幊痰母拍?并將一個用于連接數(shù)據(jù)庫,選擇數(shù)據(jù)庫和關(guān)閉數(shù)據(jù)庫連接的類組合在一起.到目前為止,除了關(guān)閉與數(shù)據(jù)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(dāng)我嘗試斷開與數(shù)據(jù)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(shù)的括號中放置connectdb方法那么簡單,但找不到正確的方法.

謝謝

解決方法:

我會在你的類中添加一個連接/鏈接變量,并使用析構(gòu)函數(shù).
這也將使您不必忘記關(guān)閉連接,因?yàn)樗鼤詣油瓿?
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(shí)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(kuò)展查詢方法,包括注入保護(hù)和任何其他幫助函數(shù).
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()合并到__construct()中,以節(jié)省額外的兩行代碼.
>添加了查詢($query)
>示例用法

如果我寫了一個錯字或錯誤,請留下建設(shè)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(jīng)過時了,因?yàn)檫@個問題仍然定期訪問,我想我會發(fā)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 />";
    }
?>