PHP-PDO连接字符串中未替换的变量 [英] PHP - Variables not replaced in PDO connection string

问题描述

奇怪的问题-我有一个正常工作的数据库类的实时副本(使用PDO).我在使用WAMPServer的计算机上有一个副本，但没有.

Strange issue - I have a live copy of a database class (using PDO) that works fine. I have a copy on my machine using WAMPServer which does not.

连接字符串如下(该类的一个片段):

The connection string is as follows (a snippet from the class):

$host = 'localhost';
$user = 'user';
$pass = 'password';
$dbname = 'my_dbname';

self::$_instance = new PDO('mysql:host=$host;dbname=$dbname', $user, $pass);

我收到的错误消息是:

Warning: PDO::__construct() [pdo.--construct]: php_network_getaddresses: getaddrinfo failed: No such host is known. in <path> on line 41

Warning: PDO::__construct() [pdo.--construct]: [2002] php_network_getaddresses: getaddrinfo failed: No such host is kn (trying to connect via tcp://$host:3306) in <path> on line 41

我不知道为什么它不能在本地运行，而在网上可以正常运行.如果我将行本身更改为以下内容，则效果很好:

I have no idea why it's not working locally whereas online its fine. If I change the line itself to the below it works fine:

self::$_instance = new PDO('mysql:host=localhost;dbname=my_dbname', $user, $pass);

谢谢:)

推荐答案

使用双引号new PDO("mysql:host=$host;dbname=$dbname", $user, $pass);，否则变量将不会插入到字符串中.另一种方式可能是

Use double quotes new PDO("mysql:host=$host;dbname=$dbname", $user, $pass); otherwise the variables will not inserted into the string. Another way could be

new PDO(sprintf('mysql:host=%s;dbname=%s', $host, $dbname), $user, $pass);

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