mysqli::__construct

mysqli::connect

mysqli_connect

(PHP 5, PHP 7, PHP 8)

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

说明

面向对象风格

public mysqli::__construct(
    ?string $hostname = null,
    ?string $username = null,
    #[\SensitiveParameter] ?string $password = null,
    ?string $database = null,
    ?int $port = null,
    ?string $socket = null
)
public mysqli::connect(
    ?string $hostname = null,
    ?string $username = null,
    #[\SensitiveParameter] ?string $password = null,
    ?string $database = null,
    ?int $port = null,
    ?string $socket = null
): bool

过程化风格

mysqli_connect(
    ?string $hostname = null,
    ?string $username = null,
    #[\SensitiveParameter] ?string $password = null,
    ?string $database = null,
    ?int $port = null,
    ?string $socket = null
): mysqli|false

Opens a connection to the MySQL Server.

参数

hostname

Can be either a host name or an IP address. When passing null, the value is retrieved from mysqli.default_host. When possible, pipes will be used instead of the TCP/IP protocol. The TCP/IP protocol is used if a host name and port number are provided together e.g. localhost:3308.

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

username

The MySQL username or null to assume the username based on the mysqli.default_user ini option.

password

The MySQL password or null to assume the password based on the mysqli.default_pw ini option.

database

The default database to be used when performing queries or null.

port

The port number to attempt to connect to the MySQL server or null to assume the port based on the mysqli.default_port ini option.

socket

The socket or named pipe that should be used or null to assume the socket based on the mysqli.default_socket ini option.

注意:

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 hostname parameter.

返回值

mysqli_connect() returns an object which represents the connection to a MySQL Server, 或者在失败时返回 false.

mysqli::connect() returns true on success 或者在失败时返回 false. Prior to PHP 8.1.0, returns null on success.

错误／异常

If mysqli error reporting is enabled (MYSQLI_REPORT_ERROR) and the requested operation fails, a warning is generated. If, in addition, the mode is set to MYSQLI_REPORT_STRICT, a mysqli_sql_exception is thrown instead.

更新日志

版本 说明
8.1.0 mysqli::connect() now returns true instead of null on success.
7.4.0 All parameters are now nullable.

示例

示例 #1 mysqli::__construct() example

面向对象风格

<?php

/* You should enable error reporting for mysqli before attempting to make a connection */
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

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

/* Set the desired charset after establishing a connection */
$mysqli->set_charset('utf8mb4');

printf("Success... %s\n", $mysqli->host_info);

过程化风格

<?php

/* You should enable error reporting for mysqli before attempting to make a connection */
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

$mysqli = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');

/* Set the desired charset after establishing a connection */
mysqli_set_charset($mysqli, 'utf8mb4');

printf("Success... %s\n", mysqli_get_host_info($mysqli));

以上示例的输出类似于：

Success... localhost via TCP/IP

示例 #2 Extending mysqli class

<?php

class FooMysqli extends mysqli {
public function __construct($host, $user, $pass, $db, $port, $socket, $charset) {
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
parent::__construct($host, $user, $pass, $db, $port, $socket);
$this->set_charset($charset);
}
}

$db = new FooMysqli('localhost', 'my_user', 'my_password', 'my_db', 3306, null, 'utf8mb4');

示例 #3 Manual error handling

If error reporting is disabled, the developer is responsible for checking and handling failures

面向对象风格

<?php

error_reporting(0);
mysqli_report(MYSQLI_REPORT_OFF);
$mysqli = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
if ($mysqli->connect_errno) {
throw new RuntimeException('mysqli connection error: ' . $mysqli->connect_error);
}

/* Set the desired charset after establishing a connection */
$mysqli->set_charset('utf8mb4');
if ($mysqli->errno) {
throw new RuntimeException('mysqli error: ' . $mysqli->error);
}

过程化风格

<?php

error_reporting(0);
mysqli_report(MYSQLI_REPORT_OFF);
$mysqli = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (mysqli_connect_errno()) {
throw new RuntimeException('mysqli connection error: ' . mysqli_connect_error());
}

/* Set the desired charset after establishing a connection */
mysqli_set_charset($mysqli, 'utf8mb4');
if (mysqli_errno($mysqli)) {
throw new RuntimeException('mysqli error: ' . mysqli_error($mysqli));
}

注释

注意:

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。

注意:

面向对象风格 only: If the connection fails, an object is still returned. To check whether the connection failed, use either the mysqli_connect_error() function or the mysqli->connect_error property as in the preceding examples.

注意:

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

注意:

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

注意:

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