mysqli::$connect_error
mysqli::debug
mysqli
PHP Manual

# mysqli::__construct

# mysqli_connect

(PHP 5)

mysqli::__construct -- mysqli_connect — Open a new connection to the MySQL server

### Description

Object oriented style

mysqli::__construct() ([ string `$host` = ini_get("mysqli.default_host") [, string `$username` = ini_get("mysqli.default_user") [, string `$passwd` = ini_get("mysqli.default_pw") [, string `$dbname` = "" [, int `$port` = ini_get("mysqli.default_port") [, string `$socket` = ini_get("mysqli.default_socket") ]]]]]] )

Procedural style

mysqli mysqli_connect ([ string `$host` = ini_get("mysqli.default_host") [, string `$username` = ini_get("mysqli.default_user") [, string `$passwd` = ini_get("mysqli.default_pw") [, string `$dbname` = "" [, int `$port` = ini_get("mysqli.default_port") [, string `$socket` = ini_get("mysqli.default_socket") ]]]]]] )

Opens a connection to the MySQL Server running on.

### Parameters

`host`

  Can be either a host name or an IP address. Passing the `NULL` value or the string "localhost" to this parameter, the local host is assumed. When possible, pipes will be used instead of the TCP/IP protocol.

  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.

`passwd`

  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 as provided or not).

`dbname`

  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 `host` parameter.

### Return Values

Returns an object which represents the connection to a MySQL Server.

### Changelog

Version | Description
--- | ---
5.3.0 | Added the ability of persistent connections.

### Examples

Example #1 mysqli::__construct() example

Object oriented style

`<?php
$mysqli = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
/*
* This is the "official" OO way to do it,
* BUT $connect_error was broken until PHP 5.2.9 and 5.3.0.
*/
if ($mysqli->connect_error) {
die('Connect Error (' . $mysqli->connect_errno . ') '
. $mysqli->connect_error);
}
/*
* Use this instead of $connect_error if you need to ensure
* compatibility with PHP versions prior to 5.2.9 and 5.3.0.
*/
if (mysqli_connect_error()) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Success... ' . $mysqli->host_info . "\n";
$mysqli->close();
?>`

Object oriented style when extending mysqli class

`<?php
class foo_mysqli extends mysqli {
public function __construct($host, $user, $pass, $db) {
parent::__construct($host, $user, $pass, $db);
if (mysqli_connect_error()) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
}
}
$db = new foo_mysqli('localhost', 'my_user', 'my_password', 'my_db');
echo 'Success... ' . $db->host_info . "\n";
$db->close();
?>`

Procedural style

`<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Success... ' . mysqli_get_host_info($link) . "\n";
mysqli_close($link);
?>`

The above examples will output:

    Success... MySQL host info: localhost via TCP/IP

### 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:

> OO syntax only: If a connection fails an object is still returned. To check if the connection failed then 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.

### See Also

- mysqli_real_connect() - Opens a connection to a mysql server
- mysqli_options() - Set options
- mysqli_connect_errno() - Returns the error code from last connect call
- mysqli_connect_error() - Returns a string description of the last connect error
- mysqli_close() - Closes a previously opened database connection

mysqli::$connect_error
mysqli::debug
mysqli
PHP Manual