使用PDO操作数据库的好处：1、PDO真正的以底层实现的统一接口操作数据库；2、PDO支持更高级的DB特性操作；3、PDO是PHP官方的PECL库，兼容性和稳定性要高于MySQL扩展；4、PDO可以防止SQL注入，确保数据库更加安全。
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。
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有预处理语句，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。
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
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