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本文介紹了簡單的 PDO 包裝器的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學習吧！

問題描述

我的 Web 應用程序目前確實執行了簡單的查詢:簡單的 CRUD 操作、計數、...

My web application currently has do execute simple queries: simple CRUD operations, counting,...

幾個月前，有人推薦我在這里為此編寫一個簡單的 PDO 包裝器(以避免每次應執行查詢時編寫 try/catch、prepare()、execute() 等).顯示了此示例方法(我進行了一些更改，以便可以在我自己的項目中使用它):

A few months ago, someone recommended me here to write a simple PDO wrapper for this (to avoid writing try/catch, prepare(), execute(), etc. each time a query should be executed). This example method was shown (I've made some changes so I could use it in my own project):

public function execute() {
    $args  = func_get_args();
    $query = array_shift($args);
    $result = false;

    try {
      $res = $this->pdo->prepare($query);
      $result = $res->execute($args);
    } catch (PDOException $e) { echo $e->getMessage(); }

    return $result;
  }

由于我需要執行更多操作(執行查詢、檢索 1 條記錄、檢索多條記錄、計算結果)，我為所有這些操作創建了一個方法:

As I need to perform more operations (executing queries, retrieving 1 record, retrieving multiple records, counting results) I created a method for all of these:

  public function getMultipleRecords() {
    $args  = func_get_args();
    $query = array_shift($args);
    $records = array();

    try {
      $res = $this->pdo->prepare($query);
      $res->execute($args);
      $records = $res->fetchAll();
    } catch (PDOException $e) { echo $e->getMessage(); }

    return $records;
  }

  public function getSingleRecord() {
    $args  = func_get_args();
    $query = array_shift($args);
    $record = array();

    try {
      $res = $this->pdo->prepare($query);
      $res->execute($args);
      $record = $res->fetch();
    } catch (PDOException $e) { echo $e->getMessage(); }

    return $record;
  }

  public function execute() {
    $args  = func_get_args();
    $query = array_shift($args);
    $result = false;

    try {
      $res = $this->pdo->prepare($query);
      $result = $res->execute($args);
    } catch (PDOException $e) { echo $e->getMessage(); }

    return $result;
  }

  public function count() {
    $args  = func_get_args();
    $query = array_shift($args);
    $result = -1;

    try {
      $res = $this->pdo->prepare($query);
      $res->execute($args);
      $result = $res->fetchColumn();
    } catch(PDOException $e) { echo $e->getMessage(); }

    return $result;
  }

如您所見，大部分代碼是相同的.每種方法只有 2 行代碼不同:$result 的初始化(我總是想返回一個值，即使查詢失敗)和獲取.我可以不使用 4 種方法，而是只編寫其中一種并傳遞一個帶有操作類型的額外參數.這樣，我可以使用 switch 語句的一堆 if/else 語句.但是，我認為代碼可能會變得混亂.這是解決這個問題的好方法嗎?如果沒有，有什么好的解決辦法?

As you see, most of the code is the same. Only 2 lines of code are different for each method: the initialisation of $result (I always want to return a value, even if the query fails) and the fetching. Instead of using 4 methods, I could write just one of them and pass an extra parameter with the type of action. That way, I could use a bunch of if/else statements of a switch statement. However, I think the code can get messy. Is this a good way for solving this problem? If not, what would be a good solution to it?

我遇到的第二個問題(這就是我現在正在研究這個類的原因)是我想將準備好的語句與 LIMIT SQL 語句一起使用.但是，這是不可能的:

The second problem I have (which is why I'm working on this class right now) is that I want to use prepared statements with the LIMIT SQL statement. However, it is not possible to do this:

$res = $pdo->prepare("SELECT * FROM table LIMIT ?");
$res->execute(array($int));

由于某種原因，變量將被引用(因此查詢將失敗)，如下所述:https://bugs.php.net/bug.php?id=40740

The variabele will be quoted for some reason (and so the query will fail), as explained here: https://bugs.php.net/bug.php?id=40740

解決方案似乎使用 bindValue() 并使用 int 數據類型作為參數:http://www.php.net/manual/de/pdostatement.bindvalue.php

The solution seems to use bindValue() and use the int datatype as a parameter: http://www.php.net/manual/de/pdostatement.bindvalue.php

我可以重寫方法來支持這一點，但我還需要使用一個額外的參數.我不能再使用 $db->e??xecute($sql, $variable1, $variable2); 因為我需要知道數據類型.

I could rewrite the method(s) to support this, but I would also need to use an extra parameter. I can't just use $db->execute($sql, $variable1, $variable2); anymore as I need to know the data type.

解決這個問題的最佳方法是什么?

What's the best way to solve this?

謝謝

推薦答案

如何使用可以鏈接的方法創建一個類(為了清楚起見，我已經刪除了錯誤檢查):

How about creating a class with methods that you can chain (for clarity, I've removed error checking):

class DB {

    private $dbh;
    private $stmt;

    public function __construct($user, $pass, $dbname) {
        $this->dbh = new PDO(
            "mysql:host=localhost;dbname=$dbname",
            $user,
            $pass,
            array( PDO::ATTR_PERSISTENT => true )
        );
    }

    public function query($query) {
        $this->stmt = $this->dbh->prepare($query);
        return $this;
    }

    public function bind($pos, $value, $type = null) {

        if( is_null($type) ) {
            switch( true ) {
                case is_int($value):
                    $type = PDO::PARAM_INT;
                    break;
                case is_bool($value):
                    $type = PDO::PARAM_BOOL;
                    break;
                case is_null($value):
                    $type = PDO::PARAM_NULL;
                    break;
                default:
                    $type = PDO::PARAM_STR;
            }
        }

        $this->stmt->bindValue($pos, $value, $type);
        return $this;
    }

    public function execute() {
        return $this->stmt->execute();
    }

    public function resultset() {
        $this->execute();
        return $this->stmt->fetchAll();
    }

    public function single() {
        $this->execute();
        return $this->stmt->fetch();
    }
}

然后您可以像這樣使用它:

You can then use it like this:

// Establish a connection.
$db = new DB('user', 'password', 'database');

// Create query, bind values and return a single row.
$row = $db->query('SELECT col1, col2, col3 FROM mytable WHERE id > ? LIMIT ?')
   ->bind(1, 2)
   ->bind(2, 1)
   ->single();

// Update the LIMIT and get a resultset.
$db->bind(2,2);
$rs = $db->resultset();

// Create a new query, bind values and return a resultset.
$rs = $db->query('SELECT col1, col2, col3 FROM mytable WHERE col2 = ?')
   ->bind(1, 'abc')
   ->resultset();

// Update WHERE clause and return a resultset.
$db->bind(1, 'def');
$rs = $db->resultset();

如果您愿意，您可以更改 bind 方法以接受數組或關聯數組，但我發現此語法非常清晰 - 它避免了必須構建數組.參數類型檢查是可選的，因為 PDO::PARAM_STR 適用于大多數值，但請注意傳遞空值時的潛在問題(請參閱 PDOStatement->bindValue 文檔中的注釋).

You could alter the bind method to accept an array or associative array if you prefer, but I find this syntax quite clear - it avoids having to build an array. The parameter type checking is optional, as PDO::PARAM_STR works for most values, but be aware of potential issues when passing null values (see comment in PDOStatement->bindValue documentation).

這篇關于簡單的 PDO 包裝器的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！

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簡單的 PDO 包裝器

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