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(PHP 5, PHP 7, PHP 8)
mysqli::__construct -- mysqli::connect -- mysqli_connect — Open a new connection to the MySQL server
面向对象风格
$hostname = ini_get("mysqli.default_host"),$username = ini_get("mysqli.default_user"),$password = ini_get("mysqli.default_pw"),$database = "",$port = ini_get("mysqli.default_port"),$socket = ini_get("mysqli.default_socket")$hostname = ini_get("mysqli.default_host"),$username = ini_get("mysqli.default_user"),$password = ini_get("mysqli.default_pw"),$database = "",$port = ini_get("mysqli.default_port"),$socket = ini_get("mysqli.default_socket")过程化风格
$hostname = ini_get("mysqli.default_host"),$username = ini_get("mysqli.default_user"),$password = ini_get("mysqli.default_pw"),$database = "",$port = ini_get("mysqli.default_port"),$socket = ini_get("mysqli.default_socket")Opens a connection to the MySQL Server.
hostname
Can be either a host name or an IP address. The local host is
assumed when passing the null value or the string "localhost" to this parameter.
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 user name.
password
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 is provided or not).
database
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.
注意:
Specifying the
socketparameter 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 thehostnameparameter.
mysqli::__construct() always returns an object which represents the connection to a MySQL Server, regardless of it being successful or not.
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 null on success 或者在失败时返回 false.
If MYSQLI_REPORT_STRICT is enabled and the attempt to connect
to the requested database fails, a mysqli_sql_exception is thrown.
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($mysqli));
以上例程的输出类似于：
Success... localhost via TCP/IP
示例 #2 Extending mysqli class
<?php
class FooMysqli extends mysqli {
public function __construct($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 theSYSTEMROOTenvironment variable won't be available and PHP will have problems loading Winsock.
