PHP PDO准备重复变量

一尘不染

PHP PDO准备重复变量

php

在编写pdo语句时，是否可以重复变量的值？我的意思是：

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

请注意，我重复“：name”名称持有者，而我只提供一次值。我该如何进行这项工作？

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2020-05-29

共1个答案

一尘不染

简单的答案是：您不能。PDO对准备好的语句使用了抽象，这有一定的局限性。不幸的是，这是一个问题，您必须使用类似的方法来解决

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

在某些情况下，例如使用某些版本的PDO /
MySQL驱动程序模拟准备好的语句，则支持重复的命名参数；但是，这不应该依赖，因为它很脆弱（例如，升级可能需要更多的工作）。

如果要支持命名参数的多个外观，则始终可以扩展PDO和PDOStatement（通过经典继承或按组成），也可以仅扩展PDOStatement，然后通过设置PDO::ATTR_STATEMENT_CLASS属性将类设置为语句类。扩展的PDOStatement（或PDO::prepare）可以提取命名的参数，查找重复项并自动生成替换项。它还将记录这些重复项。当绑定和执行方法传递一个命名参数时，它将测试该参数是否重复并将该值绑定到每个替换参数。

注意：以下示例未经测试，并且可能存在错误（一些与语句解析有关的错误在代码注释中注明）。

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);
        }
    }
}

2020-05-29