mysqli::__construct

mysqli_connect

(PHP 5)

mysqli::__construct -- mysqli_connect — Open a new connection to the MySQL server

说明

面向对象风格

mysqli::__construct() ([ string $host = ini_get("mysqli.default_host") [, string $username = ini_get("mysqli.default_user") [, string $passwd = ini_get("mysqli.default_pw") [, string $dbname = "" [, int $port = ini_get("mysqli.default_port") [, string $socket = ini_get("mysqli.default_socket") ]]]]]] )

过程化风格

mysqli mysqli_connect ([ string $host = ini_get("mysqli.default_host") [, string $username = ini_get("mysqli.default_user") [, string $passwd = ini_get("mysqli.default_pw") [, string $dbname = "" [, int $port = ini_get("mysqli.default_port") [, string $socket = ini_get("mysqli.default_socket") ]]]]]] )

Opens a connection to the MySQL Server running on.

参数

host

Can be either a host name or an IP address. Passing the NULL value or the string "localhost" to this parameter, the local host is assumed. When possible, pipes will be used instead of the TCP/IP protocol.

Prepending host by p: opens a persistent connection. mysqli_change_user() is automatically called on connections opened from the connection pool.

username

The MySQL user name.

passwd

If not provided or NULL, the MySQL server will attempt to authenticate the user against those user records which have no password only. This allows one username to be used with different permissions (depending on if a password as provided or not).

dbname

If provided will specify the default database to be used when performing queries.

port

Specifies the port number to attempt to connect to the MySQL server.

socket

Specifies the socket or named pipe that should be used.

Note:
Specifying the socket parameter will not explicitly determine the type of connection to be used when connecting to the MySQL server. How the connection is made to the MySQL database is determined by the host parameter.

返回值

Returns an object which represents the connection to a MySQL Server.

更新日志

版本	说明
5.3.0	Added the ability of persistent connections.

范例

Example #1 mysqli::__construct() example

面向对象风格


<?php
$mysqli = new mysqli('localhost', 'my_user', 'my_password', 'my_db');

/*
 * This is the "official" OO way to do it,
 * BUT $connect_error was broken until PHP 5.2.9 and 5.3.0.
 */
if ($mysqli->connect_error) {
    die('Connect Error (' . $mysqli->connect_errno . ') '
            . $mysqli->connect_error);
}

/*
 * Use this instead of $connect_error if you need to ensure
 * compatibility with PHP versions prior to 5.2.9 and 5.3.0.
 */
if (mysqli_connect_error()) {
    die('Connect Error (' . mysqli_connect_errno() . ') '
            . mysqli_connect_error());
}

echo 'Success... ' . $mysqli->host_info . "\n";

$mysqli->close();
?>

面向对象风格 when extending mysqli class


<?php

class foo_mysqli extends mysqli {
    public function __construct($host, $user, $pass, $db) {
        parent::__construct($host, $user, $pass, $db);

        if (mysqli_connect_error()) {
            die('Connect Error (' . mysqli_connect_errno() . ') '
                    . mysqli_connect_error());
        }
    }
}

$db = new foo_mysqli('localhost', 'my_user', 'my_password', 'my_db');

echo 'Success... ' . $db->host_info . "\n";

$db->close();
?>

过程化风格


<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');

if (!$link) {
    die('Connect Error (' . mysqli_connect_errno() . ') '
            . mysqli_connect_error());
}

echo 'Success... ' . mysqli_get_host_info($link) . "\n";

mysqli_close($link);
?>

以上例程会输出：

Success... MySQL host info: localhost via TCP/IP

注释

Note:
MySQLnd 总是使用服务器的默认字符集。此字符集在连接握手／认证时发送，并被 mysqlnd 使用。
Libmysqlclient 使用 my.cnf 中的默认字符集或者由在调用 mysqli_init() 之后， mysqli_real_connect() 之前先调用 mysqli_options() 来指定。

Note:
OO syntax only: If a connection fails an object is still returned. To check if the connection failed then use either the mysqli_connect_error() function or the mysqli->connect_error property as in the preceding examples.

Note:
If it is necessary to set options, such as the connection timeout, mysqli_real_connect() must be used instead.

Note:
Calling the constructor with no parameters is the same as calling mysqli_init().

Note:
Error "Can't create TCP/IP socket (10106)" usually means that the variables_order configure directive doesn't contain character E. On Windows, if the environment is not copied the SYSTEMROOT environment variable won't be available and PHP will have problems loading Winsock.

参见

mysqli_real_connect() - Opens a connection to a mysql server
mysqli_options() - Set options
mysqli_connect_errno() - Returns the error code from last connect call
mysqli_connect_error() - Returns a string description of the last connect error
mysqli_close() - 关闭先前打开的数据库连接

用户评论:

paul at mtnlist dot com (2013-06-02 08:19:16)

If you want to connect via an alternate port (other than 3306), as you might when using an ssh tunnel to another host, using "localhost" as the hostname will not work. Using 127.0.0.1 will work. Apparently, if you specify the host as "localhost", the constructor ignores the port specified as an argument to the constructor.

oleg at mastak dot fi (2013-04-19 13:02:18)

If you want to connect to local named pipe on windows and you get error "php_network_getaddresses: getaddrinfo failed: No such host is known. ", even if you using using "." as host, please check your if you are using mysqlnd driver: If this is true, then probably you need to update to version 5.4 of php: Named pipes support for Windows was added in PHP version 5.4.0. @ http://php.net/manual/en/mysqlnd.overview.php Hopefully that will save you some time.

boukeversteegh at gmail dot com (2011-04-18 06:19:36)

(php 5.3.3) If $port is a string, such as "3306", mysqli::query() will not work, even though mysqli_connect_errno() reports no error (value 0)! <?php $mysqli = new mysqli("localhost", "user","password","database", "3306"); //port is a string! $mysqli->query("SELECT 1;")->fetch_assoc(); // Fatal error: Call to a member function fetch_assoc() on a non-object ?> This is particularly strange, since mysqli::query() should return a result object, or a boolean. So, be careful when you read your port from a string or config file. Cast it to int first: <?php $port = (int)$port; ?>

Anonymous (2009-09-13 17:37:12)

If you get an error like Can't connect to MySQL server on 'localhost' (10061) and you use named pipes/socket connections (or aren't sure how you installed the MySQL server) try the following connect command: <?php mysqli_connect('.', $user_name, $password, $database_name, null, 'mysql'); ?> The '.' as hostname is absolutely necessary when using named pipes. 'localhost' won't work. 'mysql' is the standard name for the pipe/socket.

Slavyansk2.ru (2008-09-25 22:14:27)

If you have error like "Trying to clone an uncloneable object of class..." when trying connect, add record php_value zend.ze1_compatibility_mode 0 in your .htaccess file. This resolve connection problem.

chip1977 at mail dot ru (2008-01-28 04:52:17)

To specify charset in my.cnf file you just have to add skip-character-set-client-handshake directive after [mysqld] default-character-set=utf8