php PDO：调用未定义的方法 DB::query()

PDO: Call to undefined method DB::query()

提问by ritch

Trying to get to hang of PDO but not having much fun at the moment. I bet it's something really simple as well.

试图掌握 PDO，但目前没有太多乐趣。我敢打赌，这也很简单。

EDIT: What would be a better way to go about doing this? i.e instead of wrapping it in a class?

编辑：这样做的更好方法是什么？即而不是将它包装在一个类中？

classes/DB.class.php:

类/DB.class.php：

<?php

// DB.class.php

class DB {

    protected $db_name = "PDO";
    protected $db_user = "root";
    protected $db_pass = "root";
    protected $db_host = "localhost";

    // Establish Connection to Database.

    public function connect() {

        try {
            $DB = new PDO("mysql:host=$db_host;dbname=$db_name", $db_user, $db_pass);
        }
        catch (PDOException $e) {
            echo $e->getMessage();
        }

    }

}

?>

includes/global.inc.php:

包括/global.inc.php：

<?php

require_once 'classes/DB.class.php';

// Establish Connection to Database.

$db = new DB();
$db->connect();

?>

index.php:

索引.php：

<?php

require_once 'includes/global.inc.php';

$STH = $db->query("SELECT * FROM users");
echo "<pre>";
print_r($STH->fetch());

?>

采纳答案by Tomasz Kowalczyk

You don't have DB property and query()method in your DB class. Add it like this listing:

您query()的 DB 类中没有 DB 属性和方法。像这样添加它：

class DB
    {
    protected $db_name = "PDO";
    protected $db_user = "root";
    protected $db_pass = "root";
    protected $db_host = "localhost";
    protected $DB = null;

    // Establish Connection to Database.
    public function connect()
        {
        try
            {
            $this->DB = new PDO("mysql:host=".$this->db_host.";dbname=".$this->db_name."", $this->db_user, $this->db_pass);
            } 
        catch(PDOException $e)
            {
            echo $e->getMessage();
            }
        }

    public function query()
        {
        return $this->DB->query();
        }
    }

The better way would be to use some ORM library or bare PDO object - it's quite friendly.

更好的方法是使用一些 ORM 库或裸 PDO 对象 - 它非常友好。

回答by netcoder

Try this:

尝试这个：

class DB extends PDO {

    protected $db_name = "PDO";
    protected $db_user = "root";
    protected $db_pass = "root";
    protected $db_host = "localhost";

    public function __construct() {
        try {
            parent::__construct("mysql:host={$this->db_host};dbname={$this->db_name}", $this->db_user, $this->db_pass);
        } catch (PDOException $e) {
            echo $e->getMessage();
        }
    }

}

$db = new DB;
$db->query('SELECT * FROM something');

Also, I added the $thiskeyword in front of your members, because $db_nameand such were not declared in the method scope.

另外，我$this在您的成员前面添加了关键字，因为$db_name没有在方法范围内声明。

If you do not want the connection to be initiated when the object is created, you could do:

如果您不希望在创建对象时启动连接，您可以执行以下操作：

class DB extends PDO {

    protected $db_name = "PDO";
    protected $db_user = "root";
    protected $db_pass = "root";
    protected $db_host = "localhost";

    public function __construct() {
        // do nothing
    }

    public function connect() {
        try {
            parent::__construct("mysql:host={$this->db_host};dbname={$this->db_name}", $this->db_user, $this->db_pass);
        } catch (PDOException $e) {
            echo $e->getMessage();
        }
    }

}

$db = new DB;
$db->connect();
$db->query('SELECT * FROM something');

Important note:Normally, when overriding methods in children, you need to specify the same method signature as the parent (or you'll get an E_STRICT error). Fortunately, this doesn't apply to core classes, probably to allow overrides like this.

重要说明：通常，当覆盖子级中的方法时，您需要指定与父级相同的方法签名（否则会出现 E_STRICT 错误）。幸运的是，这不适用于核心类，可能允许像这样覆盖。

回答by datasage

The object instantiated as $db does not have the method query. There is probably not a need to wrap the PDO object within another object, but if you are going to do that, you need to make sure all methods are accessible.

实例化为 $db 的对象没有方法查询。可能不需要将 PDO 对象包装在另一个对象中，但是如果您打算这样做，您需要确保所有方法都可以访问。

回答by Sascha Galley

your class DB has no method query! you could do it this way:

您的类 DB 没有方法查询！你可以这样做：

<?php

    // DB.class.php

    class DB {

    protected $db_name = "PDO";
    protected $db_user = "root";
    protected $db_pass = "root";
    protected $db_host = "localhost";

    private $_db;

    // Establish Connection to Database.

    public function connect() {

        try {
            $this->_db = new PDO("mysql:host=".$this->db_host.";dbname=".$this->db_name, $this->db_user, $this->db_pass);
        }
        catch (PDOException $e) {
            echo $e->getMessage();
        }

    }

    public function __call($name, array $arguments) {

        if(method_exists($this->_db, $name)){
            try{
                return call_user_func_array(array(&$this->_db, $name), $arguments);
            }
            catch(Exception $e){
                throw new Exception('Database Error: "'.$name.'" does not exists');
            }
         }
     }

}

?>

With the magic function __call()you can pass all functions that PDO supports to your newly created PDO Object.

使用魔法函数，__call()您可以将 PDO 支持的所有函数传递给您新创建的 PDO 对象。