mysqli::__construct
(PHP 5, PHP 7, PHP 8)
Open a new connection to the MySQL server
Description
Oop
Procedural
Opens a connection to the MySQL Server.
Parameters
hostnameCan 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.usernameThe MySQL username or null to assume the username based on the mysqli.default_user ini option.
passwordThe MySQL password or null to assume the password based on the mysqli.default_pw ini option.
databaseThe default database to be used when performing queries or null.
portThe port number to attempt to connect to the MySQL server or null to assume the port based on the mysqli.default_port ini option.
socketThe socket or named pipe that should be used or null to assume the socket based on the mysqli.default_socket ini option.
NoteSpecifying 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.
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, Falseforfailure.
mysqli::connect returns true on successFalseforfailure. Prior to PHP 8.1.0, returns null on success.
Errors/Exceptions Conditionalexception
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
mysqli::__construct example
Oop
<?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
<?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($mysqli));Similar
Success... localhost via TCP/IPExtending mysqli class
<?php
class FooMysqli extends mysqli {
public function __construct($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');Manual error handling
If error reporting is disabled, the developer is responsible for checking and handling failures
Oop
<?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
<?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
Oop 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.