PHP PDO的setAttribute函数

数据库的连接：

 $dsn = 'mysql:host=127.0.0.1;port=3306;dbname=cardslg';
 $username = 'root';
 $password = '';
 $options = array(
     PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES utf8',
 );
 $pdo = new PDO($dsn,$username,$password,$options);

 $stmt = $pdo->prepare("SELECT * FROM card_users");

1.PDO::ATTR_CASE ：强制列名为指定的大小写。

 1)PDO::CASE_UPPER ：强制列名大写。

 $pdo->setAttribute(PDO::ATTR_CASE,PDO::CASE_UPPER);
 $stmt = $pdo->prepare("SELECT * FROM card_users");
 $stmt->setFetchMode(PDO::FETCH_OBJ);
 $stmt->execute();
 $queries = $stmt->fetch();

 file_put_contents("log.txt",print_r($queries,true));

结果：

 stdClass Object
 (
     [ID] => 1
     [USER_NAME] => lvpeilin
     [VIP] => 10
     [CONSORTIUM_ID] => 1
     [CREATED_AT] => 2016-12-16 11:55:30
 )

2)PDO::CASE_LOWER ：强制列名小写。

 $pdo->setAttribute(PDO::ATTR_CASE,PDO::CASE_LOWER);
 $stmt = $pdo->prepare("SELECT * FROM card_users");
 $stmt->setFetchMode(PDO::FETCH_OBJ);
 $stmt->execute();
 $queries = $stmt->fetch();

 file_put_contents("log.txt",print_r($queries,true));

结果：

 stdClass Object
 (
     [id] => 1
     [user_name] => lvpeilin
     [vip] => 10
     [consortium_id] => 1
     [created_at] => 2016-12-16 11:55:30
 )

3）PDO::CASE_NATURAL ：保留数据库驱动返回的列名。

 $pdo->setAttribute(PDO::ATTR_CASE,PDO::CASE_LOWER);
 $stmt = $pdo->prepare("SELECT * FROM card_users");
 $stmt->setFetchMode(PDO::FETCH_OBJ);
 $stmt->execute();
 $queries = $stmt->fetch();

结果：

 stdClass Object
 (
     [id] => 1
     [user_name] => lvpeilin
     [vip] => 10
     [consortium_id] => 1
     [created_at] => 2016-12-16 11:55:30
 )