問題描述

在編寫 pdo 語句時(shí)，是否可以重復(fù)變量的值?我的意思是:

While writing a pdo statement, is it possible to repeat the value of a variable? I mean:

$query = "UPDATE users SET firstname = :name WHERE firstname = :name";
$stmt = $dbh -> prepare($query);
$stmt -> execute(array(":name" => "Jackie"));

請(qǐng)注意，我重復(fù)了 ":name" 名稱，而我只提供了一次該值.我怎樣才能做到這一點(diǎn)?

Please note that I repeat the ":name" nameholder whereas I provide the value only once. How can I make this work?

推薦答案

簡單的答案是:你不能.PDO 對(duì)準(zhǔn)備好的語句使用抽象，但有一些限制.不幸的是，這是一個(gè)，您必須使用類似

The simple answer is: You can't. PDO uses an abstraction for prepared statements which has some limitations. Unfortunately this is one, you have to work-around using something like

$query = "UPDATE users SET firstname = :name1 WHERE firstname = :name2";
$stmt = $dbh -> prepare($query);
$stmt -> execute(array(":name1" => "Jackie", ":name2" => "Jackie"));

在某些情況下，例如使用某些版本的 PDO/MySQL 驅(qū)動(dòng)程序模擬準(zhǔn)備好的語句，支持重復(fù)命名參數(shù)；但是，不應(yīng)依賴它，因?yàn)樗艽嗳?例如，它會(huì)使升級(jí)需要更多工作).

In certain cases, such as emulated prepared statements with some versions of the PDO/MySQL driver, repeated named parameters are supported; however, this shouldn't be relied upon, as it's brittle (it can make upgrades require more work, for example).

如果你想支持一個(gè)命名參數(shù)的多次出現(xiàn)，你總是可以擴(kuò)展 PDO 和 PDOStatement(通過經(jīng)典繼承或通過組合)，或者只是 PDOStatement 并通過設(shè)置 PDO::ATTR_STATEMENT_CLASS 屬性將您的類設(shè)置為語句類.擴(kuò)展的 PDOStatement(或 PDO::prepare)可以提取命名參數(shù)，查找重復(fù)并自動(dòng)生成替換.它還會(huì)記錄這些重復(fù)項(xiàng).bind 和 execute 方法在傳遞命名參數(shù)時(shí)會(huì)測試該參數(shù)是否重復(fù)并將值綁定到每個(gè)替換參數(shù).

If you want to support multiple appearances of a named parameter, you can always extend PDO and PDOStatement (by classical inheritance or by composition), or just PDOStatement and set your class as the statement class by setting the PDO::ATTR_STATEMENT_CLASS attribute. The extended PDOStatement (or PDO::prepare) could extract the named parameters, look for repeats and automatically generate replacements. It would also record these duplicates. The bind and execute methods, when passed a named parameter, would test whether the parameter is repeated and bind the value to each replacement parameter.

注意:以下示例未經(jīng)測試，可能存在錯(cuò)誤(一些與語句解析相關(guān)的在代碼注釋中注明).

Note: the following example is untested and likely has bugs (some related to statement parsing are noted in code comments).

class PDO_multiNamed extends PDO {
    function prepare($stmt) {
        $params = array_count_values($this->_extractNamedParams());
        # get just named parameters that are repeated
        $repeated = array_filter($params, function ($count) { return $count > 1; });
        # start suffixes at 0
        $suffixes = array_map(function ($x) {return 0;}, $repeated);
        /* Replace repeated named parameters. Doesn't properly parse statement,
         * so may replacement portions of the string that it shouldn't. Proper
         * implementation left as an exercise for the reader.
         *
         * $param only contains identifier characters, so no need to escape it
         */
        $stmt = preg_replace_callback(
            '/(?:' . implode('|', array_keys($repeated)) . ')(?=W)/', 
            function ($matches) use (&$suffixes) {
                return $matches[0] . '_' . $suffixes[$matches[0]]++;
            }, $stmt);
        $this->prepare($stmt, 
                       array(
                           PDO::ATTR_STATEMENT_CLASS => array('PDOStatement_multiNamed', array($repeated)))
            );
    }

    protected function _extractNamedParams() {
        /* Not actually sufficient to parse named parameters, but it's a start.
         * Proper implementation left as an exercise.
         */
        preg_match_all('/:w+/', $stmt, $params);
        return $params[0];
    }
}

class PDOStatement_multiNamed extends PDOStatement {
    protected $_namedRepeats;

    function __construct($repeated) {
        # PDOStatement::__construct doesn't like to be called.
        //parent::__construct();
        $this->_namedRepeats = $repeated;
    }

    /* 0 may not be an appropriate default for $length, but an examination of
     * ext/pdo/pdo_stmt.c suggests it should work. Alternatively, leave off the
     * last two arguments and rely on PHP's implicit variadic function feature.
     */
    function bindParam($param, &$var, $data_type=PDO::PARAM_STR, $length=0, $driver_options=array()) {
        return $this->_bind(__FUNCTION__, $param, func_get_args());
    }

    function bindValue($param, $var, $data_type=PDO::PARAM_STR) {
        return $this->_bind(__FUNCTION__, $param, func_get_args());
    }

    function execute($input_parameters=NULL) {
        if ($input_parameters) {
            $params = array();
            # could be replaced by array_map_concat, if it existed
            foreach ($input_parameters as $name => $val) {
                if (isset($this->_namedRepeats[$param])) {
                    for ($i=0; $i < $this->_namedRepeats[$param], ++$i) {
                        $params["{$name}_{$i}"] = $val;
                    }
                } else {
                    $params[$name] = $val;
                }
            }
            return parent::execute($params);
        } else {
            return parent::execute();
        }
    }

    protected function _bind($method, $param, $args) {
        if (isset($this->_namedRepeats[$param])) {
            $result = TRUE;
            for ($i=0; $i < $this->_namedRepeats[$param], ++$i) {
                $args[0] = "{$param}_{$i}";
                # should this return early if the call fails?
                $result &= call_user_func_array("parent::$method", $args);
            }
            return $result;
        } else {
            return call_user_func_array("parent::$method", $args);
        }
    }
}

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