使用PDO操作数据库的好处

PDO一是PHP数据对象（PHP Data Object）的缩写。

并不能使用PDO扩展本身执行任何数据库操作，必须使用一个database-specific PDO driver（针对特定数据库的PDO驱动）访问数据库服务器。
PDO并不提供数据库抽象，它并不会重写SQL或提供数据库本身缺失的功能，如果你需要这种功能，你需要使用一个更加成熟的抽象层。
PDO需要PHP5核心OO特性的支持，所以它无法运行于之前的PHP版本。
http://baike.baidu.com/view/1278977.htm

PDO有非常多的操作却是MySQL扩展库所不具备的：

1:PDO真正的以底层实现的统一接口数库操作接口，不管后端使用的是何种数据库，如果代码封装好了以后，应用层调用基本上差不多的，当后端数据库更换了以后，应用层代码基本不用修改.

2:PDO支持更高级的DB特性操作，如：存储过程的调度等,mysql原生库是不支持的.

3:PDO是PHP官方的PECL库，兼容性稳定性必然要高于MySQL Extension,可以直接使用 pecl upgrade pdo 命令升级.

4:PDO可以防止SQL注入，确保数据库更加安全
PDO 防止SQL注入的原理
http://www.myhack58.com/Article/60/61/2015/63168.htm

预处理语句
使用语句预处理将帮助你免于SQL注入攻击。

一条预处理语句是一条预编译的 SQL 语句，它可以使用多次，每次只需将数据传至服务器。其额外优势在于可以对使用占位符的数据进行安全处理，防止SQL注入攻击。
http://www.php100.com/html/itnews/PHPxinwen/2013/0618/13555.html

5.根据PHP官方计划，PHP6正式到来之时，数据库链接方式统一为PDO。但是总有一小撮顽固分子，趁PHP官方还没正式统一时，还用老式的MYSQL驱动链接数据库。即使现在有部分程序改用Mysqli/pdo，只要没用到预编译，均和老式的Mysql驱动没多大区别。在此，我就不点评国内的PHP生态环境了。
回归主题，为什么说PHP必须要用PDO？除了官方要求之外，我认为作为PHP程序员，只要你目前是做开发的话，那么请选择用PDO的程序/框架！PDO除了安全和万金油式数据库链接，还有一点是我目前觉得非常好用的！下面我就用我最近的切身体会来说。
业务环境：公司某老架构，数据库设计的人员太菜了，设计过程完全没有按照数据库范式进行。各种表中使用大量的序列化形式保存（补充：json同理）。
出现问题：销售的客服反馈，网站某用户在编辑地址时，Mysql报错了。
问题猜想：不用说了。肯定是引号，反斜杠引起序列化入库不正常。
http://zhidao.baidu.com/question/1541430860923158627

6.安装配置及测试
在windows下进行有关pdo测试的时候，php.ini中的extension_dir的值要填为pdo*.dll的路径，否则无法运行pdo的相关程序。
; Directory in which the loadable extensions (modules) reside.
extension_dir = "E:\www\php5\ext"

 <?php
 $host = 'localhost';
 $user = 'root';
 $password = 'develop';
 $dbname = '99game';

 $dbh = new PDO("mysql:host=$host;dbname=$dbname", $user, $password); 

 //=======================================================
 //例子 1. Execute a prepared statement with named placeholders
 /* Execute a prepared statement by binding PHP variables */
 $user_id = 1;
 $email = 'caihf_73940@qq.com';
 $sth = $dbh->prepare('SELECT user_id,email,token FROM 99game_user
     WHERE user_id = :user_id AND email = :email');
 $sth->bindParam(':user_id', $user_id, PDO::PARAM_INT);
 $sth->bindParam(':email', $email, PDO::PARAM_STR, 30);
 $sth->execute();
 $result = $sth->fetch(PDO::FETCH_ASSOC);
 print_r($result);
 print("<br />\n");

 //例子 2. Execute a prepared statement with question mark placeholders
 /* Execute a prepared statement by binding PHP variables */
 $user_id = 2;
 $email = 'caihuafeng1@gmail.com';
 $sth = $dbh->prepare('SELECT user_id,email,token FROM 99game_user
     WHERE user_id = ? AND email = ?');
 $sth->bindParam(1, $user_id, PDO::PARAM_INT);
 $sth->bindParam(2, $email, PDO::PARAM_STR, 30);
 $sth->execute();
 $result = $sth->fetch(PDO::FETCH_ASSOC);
 print_r($result);
 print("<br />\n");

 print "<hr />\n";
  //=======================================================

 //=======================================================
 $sth = $dbh->prepare("SELECT user_id,email,token FROM 99game_user limit 10");
 $sth->execute();

 /* 运用 PDOStatement::fetch 风格 */
 print("PDO::FETCH_ASSOC: ");
 print("Return next row as an array indexed by column name<br />\n");
 $result = $sth->fetch(PDO::FETCH_ASSOC);
 print_r($result);
 print("<br />\n");
 print("\n");

 print("PDO::FETCH_BOTH: ");
 print("Return next row as an array indexed by both column name and number<br />\n");
 $result = $sth->fetch(PDO::FETCH_BOTH);
 print_r($result);
 print("<br />\n");
 print("\n");

 print("PDO::FETCH_LAZY: ");
 print("Return next row as an anonymous object with column names as properties<br />\n");
 $result = $sth->fetch(PDO::FETCH_LAZY);
 print_r($result);
 print("<br />\n");
 print("\n");

 print("PDO::FETCH_OBJ: ");
 print("Return next row as an anonymous object with column names as properties<br />\n");
 $result = $sth->fetch(PDO::FETCH_OBJ);
 print_r($result);
 print 'user_id:' . $result->user_id;
 print("<br />\n");
 print("\n");

 print "<hr />\n";
 //=======================================================

 //=======================================================
 function readDataForwards($dbh) {
   $sql = 'SELECT user_id,email,token FROM 99game_user limit 10';
   try {
     $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR, PDO::CURSOR_SCROLL));
     $stmt->execute();
     while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_NEXT)) {
       $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "<br />\n";
       print $data;
     }
     $stmt = null;
   }
   catch (PDOException $e) {
     print $e->getMessage();
   }
 }

 function readDataBackwards($dbh) {
   $sql = 'SELECT user_id,email,token FROM 99game_user limit 10';
   try {
     $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL));
     $stmt->execute();
     $row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST);
     do {
       $data = $row[0] . "\t" . $row[1] . "\t" . $row[2] . "<br />\n";
       print $data;
     } while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));
     $stmt = null;
   }
   catch (PDOException $e) {
     print $e->getMessage();
   }
 }

 print "Reading forwards:<br />\n";
 readDataForwards($dbh);

 print "<hr />\n";

 print "Reading backwards:<br />\n";
 //下面的数据没有按照想像中的倒排输出，暂时不知道什么原因，php.net官方手册中的例子也是这么写的
 readDataBackwards($dbh);
 //=======================================================
 ?>

以上测试程序输出如下：

Array
(
[user_id] => 1
[email] => caihf_73940@qq.com
[token] => 123token456_73940
)

Array
(
[user_id] => 2
[email] => caihuafeng1@gmail.com
[token] => 33fadfasdfadsf
)

PDO::FETCH_ASSOC: Return next row as an array indexed by column name
Array
(
[user_id] => 1
[email] => caihf_73940@qq.com
[token] => 123token456_73940
)

PDO::FETCH_BOTH: Return next row as an array indexed by both column name and number
Array
(
[user_id] => 2
[0] => 2
[email] => caihuafeng1@gmail.com
[1] => caihuafeng1@gmail.com
[token] => 33fadfasdfadsf
[2] => 33fadfasdfadsf
)

PDO::FETCH_LAZY: Return next row as an anonymous object with column names as properties
PDORow Object
(
[queryString] => SELECT user_id,email,token FROM 99game_user limit 10
[user_id] => 3
[email] => caihf_61039@qq.com
[token] => 123token456_61039
)

PDO::FETCH_OBJ: Return next row as an anonymous object with column names as properties
stdClass Object
(
[user_id] => 6
[email] => aa1@aa.com
[token] => cU8ady73epcmf54o7W0q1F0f8R3b2y4d
)
user_id:6

Reading forwards:
1 caihf_73940@qq.com 123token456_73940
2 caihuafeng1@gmail.com 33fadfasdfadsf
3 caihf_61039@qq.com 123token456_61039
6 aa1@aa.com cU8ady73epcmf54o7W0q1F0f8R3b2y4d
7 caihuafengqq@gmail.com 1wcl3j1a92bgc6eb8Y9rcQbjen5I8f7F
8 caihuafeng@163.com 90debU1x3ddWdSdc239hdF2t1AeScf3w
9 caihuafeng@gmail.com 1V1D8xao3O9m1mdq5706716kbx5u6n58
10 test@test.com b28de59ddc824ed8a8556514dd83c348
11 test2@test2.com 965e5873e6dbba4af57b96dfe0b027e7
12 caihf@qq.com_69054 123token456_69054

Reading backwards:
1 caihf_73940@qq.com 123token456_73940
2 caihuafeng1@gmail.com 33fadfasdfadsf
3 caihf_61039@qq.com 123token456_61039
6 aa1@aa.com cU8ady73epcmf54o7W0q1F0f8R3b2y4d
7 caihuafengqq@gmail.com 1wcl3j1a92bgc6eb8Y9rcQbjen5I8f7F
8 caihuafeng@163.com 90debU1x3ddWdSdc239hdF2t1AeScf3w
9 caihuafeng@gmail.com 1V1D8xao3O9m1mdq5706716kbx5u6n58
10 test@test.com b28de59ddc824ed8a8556514dd83c348
11 test2@test2.com 965e5873e6dbba4af57b96dfe0b027e7
12 caihf@qq.com_69054 123token456_69054

延伸阅读：
http://www.baidu.com/s?wd=php%20pdo%20%E4%BC%98%E7%82%B9
http://www.sogou.com/web?query=php%20pdo%20优点
https://www.so.com/s?q=php%20pdo%20%E4%BC%98%E7%82%B9
http://www.open-open.com/lib/view/open1419950418859.html
PHP5中PDO的简单使用
http://blog.csdn.net/leo115/article/details/7538983

php pdo操作数据库
http://www.cnblogs.com/yujon/p/5476176.html

为什么 PHP 应该使用 PDO 方式访问数据库
http://www.php100.com/html/itnews/PHPxinwen/2013/0618/13555.html

PDO预处理语句PDOStatement对象使用总结
http://www.jb51.net/article/57609.htm