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 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 true on success or false on failure.
Prior to PHP 8.1.0, returns null on success.
As of PHP 8.5.0, calling the constructor on an already-constructed object
throws an Error.
Changelog
Version
Description
8.5.0
Calling the constructor on an already-constructed object now throws
an Error.
8.1.0
mysqli::connect() now returns true instead of null on success.
7.4.0
All parameters are now nullable.
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.
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.
mysqli::$connect_error
mysqli