[kohana] kohana3.2，如何兼容PDO数据库连接方式

由于历史原因，有个kohana3.2的站点需要搬迁到php5.5上来，但php5.5已经不支持mysql_connect()这个函数了，只能使用PDO来连接数据库。

但换上PDO之后，报了这个的一个错：

Kohana_Exception [ 0 ]: Database method list_columns is not supported by Kohana_Database_PDO

居然这么恶心的事情都出现 -_-!

经过一轮google，终于找到解决方案了。

1. 在你的MODPATH或者APPPATH，创建新文件，classes/Database/PDO/MySQL.php，代码如下

<?php

/*
 * PHP version 5.5
 *
 * @copyright  Copyright (c) 2012-2015 友客OA Inc. (http://www.yokeoa.com)
 * @link       http://www.yokeoa.com
 * @license    友客OA版权所有
 */

/**
 * 我是类描述信息哦！
 *
 * @author  birdylee <birdylee_cn@163.com>
 * @since   2015年00月26日
 * @version 1.0
 *
 */
defined('SYSPATH') or die('No direct script access.');

class Database_PDO_MySQL extends Database_PDO
{
    public function list_columns($table, $like = NULL, $add_prefix = TRUE)
    {
        // Quote the table name
        $table = ($add_prefix === TRUE) ? $this->quote_table($table) : $table;

        if (is_string($like)) {
            // Search for column names
            $result = $this->query(Database::SELECT, 'SHOW FULL COLUMNS FROM ' . $table . ' LIKE ' . $this->quote($like), FALSE);
        } else {
            // Find all column names
            $result = $this->query(Database::SELECT, 'SHOW FULL COLUMNS FROM ' . $table, FALSE);
        }

        $count = 0;
        $columns = array();
        foreach ($result as $row) {
            list($type, $length) = $this->_parse_type($row['Type']);

            $column = $this->datatype($type);

            $column['column_name'] = $row['Field'];
            $column['column_default'] = $row['Default'];
            $column['data_type'] = $type;
            $column['is_nullable'] = ($row['Null'] == 'YES');
            $column['ordinal_position'] = ++$count;

            switch ($type) { //was $column['type']
                case 'float':
                    if (isset($length)) {
                        list($column['numeric_precision'], $column['numeric_scale']) = explode(',', $length);
                    }
                    break;
                case 'int':
                    if (isset($length)) {
                        // MySQL attribute
                        $column['display'] = $length;
                    }
                    break;
                case 'string':
                    switch ($column['data_type']) {
                        case 'binary':
                        case 'varbinary':
                            $column['character_maximum_length'] = $length;
                            break;
                        case 'char':
                        case 'varchar':
                            $column['character_maximum_length'] = $length;
                        case 'text':
                        case 'tinytext':
                        case 'mediumtext':
                        case 'longtext':
                            $column['collation_name'] = $row['Collation'];
                            break;
                        case 'enum':
                        case 'set':
                            $column['collation_name'] = $row['Collation'];
                            $column['options'] = explode('\',\'', substr($length, 1, -1));
                            break;
                    }
                    break;
            }

            // MySQL attributes
            $column['comment'] = $row['Comment'];
            $column['extra'] = $row['Extra'];
            $column['key'] = $row['Key'];
            $column['privileges'] = $row['Privileges'];

            $columns[$row['Field']] = $column;
        }

        return $columns;
    }

}

2. 你需要设置使用新的驱动类，%path%/database/config/database.php，将'type'由PDO换成PDO_MySQL

    'default' => array
        (
        'type' => 'PDO_MySQL',
        'connection' => array(
            'dsn' => 'mysql:dbname=test;host=127.0.0.1',
            'username' => 'root',
            'password' => '123456',
            'persistent' => FALSE,
        ),
        'table_prefix' => '',
        'charset' => 'utf8',
        'caching' => FALSE,
    ),