Copyright 1997-2022 the PHP Documentation Group.
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 void 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"));
Procedural style
mysqli|false 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"));
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.
NoteSpecifying 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 thehostname
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 3.37 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($mysqli));
The above examples will output something similar to:
Success... localhost via TCP/IP
Example 3.38 Extending mysqli class
<?php
class FooMysqli extends mysqli {
public function __construct($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 3.39 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
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
.
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.
If it is necessary to set options, such as the connection
timeout,
mysqli_real_connect
must be used instead.
Calling the constructor with no parameters is the same as
calling
mysqli_init
.
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.
See Also
mysqli_real_connect
|
mysqli_options
|
mysqli_connect_errno
|
mysqli_connect_error
|
mysqli_close
|