(PHP 5, PHP 7, PHP 8)
mysqli::__construct -- mysqli::connect -- mysqli_connect — Open a new connection to the MySQL server
Object-oriented style
$hostname
= null
,$username
= null
,$password
= null
,$database
= null
,$port
= null
,$socket
= null
$hostname
= null
,$username
= null
,$password
= null
,$database
= null
,$port
= null
,$socket
= null
Procedural style
$hostname
= null
,$username
= null
,$password
= null
,$database
= null
,$port
= null
,$socket
= null
Opens a connection to the MySQL Server.
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.
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 thehostname
parameter.
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.
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.
Version | Description |
---|---|
7.4.0 | All parameters are now nullable. |
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));
}
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 theSYSTEMROOT
environment variable won't be available and PHP will have problems loading Winsock.