<?php/** * 声明一个数组存放数据库链接信息 */ $C = array();/** * 在数据库链接信息数组中存放相关信息 */ $C[‘DB_HOST‘] = ‘localhost‘; $C[‘DB_USER‘] = ‘root‘;  $C[‘DB_PASS‘] = ‘123456‘;  $C[‘DB_NAME‘] = ‘db_test‘;  /**  * 循环生成常量  */ foreach ($C as $name => $val) {     define($name , $val); } /**  * 用PDO链接数据库  */ $dbo = new PDO("mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . "","" . DB_USER . "","" . DB_PASS . "") or die("数据库链接失败");  /**  * 试着写一个链接数据库的例子  */ try{	 $rs = $dbo -> prepare("select * from `test`");  $rs->execute();  $results = $rs->FETCHALL(PDO::FETCH_ASSOC);  $dbo = null;  print_r($results);}catch( Exception $e){	print $e->getMessage();	exit;}/*End of file DB.class.php*/