PHP Manual
mysqli
Open a new connection to the MySQL server

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

Description

Object-oriented style

public mysqli::__construct(
    string $hostname = ini_get("mysqli.default_host"),
    string $username = ini_get("mysqli.default_user"),
    string $password = ini_get("mysqli.default_pw"),
    string $database = "",
    int $port = ini_get("mysqli.default_port"),
    string $socket = ini_get("mysqli.default_socket")
)

public mysqli::connect(
    string $hostname = ini_get("mysqli.default_host"),
    string $username = ini_get("mysqli.default_user"),
    string $password = ini_get("mysqli.default_pw"),
    string $database = "",
    int $port = ini_get("mysqli.default_port"),
    string $socket = ini_get("mysqli.default_socket")
): void

Procedural style

mysqli_connect(
    string $hostname = ini_get("mysqli.default_host"),
    string $username = ini_get("mysqli.default_user"),
    string $password = ini_get("mysqli.default_pw"),
    string $database = "",
    int $port = ini_get("mysqli.default_port"),
    string $socket = ini_get("mysqli.default_socket")
): mysqli|false

Opens a connection to the MySQL Server.

Parameters

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.

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 hostname parameter.

Return Values

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, or false on failure.

mysqli::connect() returns null on success or false on failure.

Errors/Exceptions

If MYSQLI_REPORT_STRICT is enabled and the attempt to connect to the requested database fails, a mysqli_sql_exception is thrown.

Examples

Example #1 mysqli::__construct() example

Object-oriented style


<?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);

Procedural style


<?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));

The above examples will output something similar to:

Success... localhost via TCP/IP

Example #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');

Example #3 Manual error handling

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

Object-oriented style


<?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);
}

Procedural style


<?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));
}

Notes

Note:
MySQLnd always assumes the server default charset. This charset is sent during connection hand-shake/authentication, which mysqlnd will use.
Libmysqlclient uses the default charset set in the my.cnf or by an explicit call to mysqli_options() prior to calling mysqli_real_connect(), but after mysqli_init().

Note:
Object-oriented style 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.

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.