我正在尝试移植在此页面mysql_...上找到的数据库备份脚本，因为它会引发已弃用的警告。
到目前为止，我的努力如下，但脚本向我抛出了几个我不知道如何解决的错误。我对 PHP 只是稍微熟悉，所以我很可能在这里犯了初学者的错误。
抛出的错误是：
Notice: Undefined variable: db in ......../index.php on line 109 Fatal error: Call to a member function query() on a non-object in ......../index.php on line 109
第 109 行是（并标有 // * ** * ** *）：
foreach( $db->query('SHOW TABLES') as $row )
我一直在玩public/ protected(for initializeDatabase) 和global(for $db) 关键字，但我不确定这是原因还是我做错了。
谁能很容易地发现我在这里做错了什么？
<?php
/**
* This file contains the Backup_Database class wich performs
* a partial or complete backup of any given MySQL database
* @author Daniel López Azaña <http://www.daniloaz.com>
* @version 1.0
*/
/**
* Changes by jippie:
* ereg_replace("\n","\\n",$row[$j]); => preg_replace( '/\n/ , "\\n" , $row[$j] );
* mysql_... => PDO
*/
// Report all errors
error_reporting(E_ALL);
/**
* Define database parameters here
*/
define("DB_USER", 'username');
define("DB_PASSWORD", 'password');
define("DB_NAME", 'database');
define("DB_HOST", 'localhost');
define("OUTPUT_DIR", 'cache');
define("TABLES", '*');
/**
* Instantiate Backup_Database and perform backup
*/
$backupDatabase = new Backup_Database(DB_HOST, DB_USER, DB_PASSWORD, DB_NAME);
$status = $backupDatabase->backupTables(TABLES, OUTPUT_DIR) ? 'OK' : 'KO';
echo "<br /><br /><br />Backup result: ".$status;
/**
* The Backup_Database class
*/
class Backup_Database {
/**
* Host where database is located
*/
var $host = '';
/**
* Username used to connect to database
*/
var $username = '';
/**
* Password used to connect to database
*/
var $passwd = '';
/**
* Database to backup
*/
var $dbName = '';
/**
* Database charset
*/
var $charset = '';
/**
* Constructor initializes database
*/
function Backup_Database($host, $username, $passwd, $dbName, $charset = 'utf8')
{
$this->host = $host;
$this->username = $username;
$this->passwd = $passwd;
$this->dbName = $dbName;
$this->charset = $charset;
$this->initializeDatabase();
}
protected function initializeDatabase()
{
$db = new PDO("mysql:host=$this->host;dbname=$this->dbName;charset=$this->charset", $this->username, $this->passwd );
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
/* JPH: mysql_... is deprecated
* $conn = mysql_connect($this->host, $this->username, $this->passwd);
* mysql_select_db($this->dbName, $conn);
* if (! mysql_set_charset ($this->charset, $conn))
* {
* mysql_query('SET NAMES '.$this->charset);
* }
*/
}
/**
* Backup the whole database or just some tables
* Use '*' for whole database or 'table1 table2 table3...'
* @param string $tables
*/
public function backupTables($tables = '*', $outputDir = '.')
{
try
{
/**
* Tables to export
*/
if($tables == '*')
{
$tables = array();
// $result = mysql_query('SHOW TABLES');
// while($row = mysql_fetch_row($result))
// *******
foreach( $db->query('SHOW TABLES') as $row )
{
$tables[] = $row[0];
}
}
else
{
$tables = is_array($tables) ? $tables : explode(',',$tables);
}
$sql = 'CREATE DATABASE IF NOT EXISTS '.$this->dbName.";\n\n";
$sql .= 'USE '.$this->dbName.";\n\n";
/**
* Iterate tables
*/
foreach($tables as $table)
{
echo "Backing up ".$table." table...";
// $result = mysql_query('SELECT * FROM '.$table);
// $numFields = mysql_num_fields($result);
$result = $db->query( 'SELECT * FROM ' . $table );
$numFields = $result->columnCount();
$sql .= 'DROP TABLE IF EXISTS '.$table.';';
// $row2 = mysql_fetch_row(mysql_query('SHOW CREATE TABLE '.$table));
$result2 = $db->query( 'SHOW CREATE TABLE ' . $table );
$row2 = $result2->fetch();
$sql.= "\n\n".$row2[1].";\n\n";
for ($i = 0; $i < $numFields; $i++)
{
// while($row = mysql_fetch_row($result))
while( $row = $result2->fetch() )
{
$sql .= 'INSERT INTO '.$table.' VALUES(';
for($j=0; $j<$numFields; $j++)
{
$row[$j] = addslashes($row[$j]);
$row[$j] = preg_replace( '/\n/' , "\\n" , $row[$j] );
if (isset($row[$j]))
{
$sql .= '"'.$row[$j].'"' ;
}
else
{
$sql.= '""';
}
if ($j < ($numFields-1))
{
$sql .= ',';
}
}
$sql.= ");\n";
}
}
$sql.="\n\n\n";
echo " OK" . "<br />";
}
}
catch (Exception $e)
{
var_dump($e->getMessage());
return false;
}
return $this->saveFile($sql, $outputDir);
}
/**
* Save SQL to file
* @param string $sql
*/
protected function saveFile(&$sql, $outputDir = '.')
{
if (!$sql) return false;
try
{
$handle = fopen($outputDir.'/db-backup-'.$this->dbName.'-'.date("Ymd-His", time()).'.sql','w+');
fwrite($handle, $sql);
fclose($handle);
}
catch (Exception $e)
{
var_dump($e->getMessage());
return false;
}
return true;
}
}