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- PHP Manual
- Function Reference
- Database Extensions
- Vendor Specific Database Extensions
- MySQL
- MySQLi
- mysqli
(PHP 5, PHP 7, PHP 8)
mysqli::__construct -- mysqli::connect -- mysqli_connect — Open a new connection to the MySQL server
Description
Object-oriented style
public mysqli::__construct(
?string $hostname
= null
,
?string $username
= null
,
#[\SensitiveParameter] ?string $password
= null
,
?string $database
= null
,
?int $port
= null
,
?string $socket
= null
)
public mysqli::connect(
?string $hostname
= null
,
?string $username
= null
,
#[\SensitiveParameter] ?string $password
= null
,
?string $database
= null
,
?int $port
= null
,
?string $socket
= null
): bool
Procedural style
mysqli_connect(
?string $hostname
= null
,
?string $username
= null
,
#[\SensitiveParameter] ?string $password
= null
,
?string $database
= null
,
?int $port
= null
,
?string $socket
= null
): mysqli|false
Opens a connection to the MySQL Server.
Parameters
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.
Return Values
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.
Errors/Exceptions
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.
Changelog
Version | Description |
---|---|
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 outputsomething similar to:
Success... localhost via TCP/IP
Example #2 Extending mysqli class
<?phpclass 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
error_reporting<?php
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
error_reporting<?php
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 connectionhand-shake/authentication, which mysqlnd will use.
Libmysqlclient uses the default charset set in themy.cnf or by an explicit call to mysqli_options() prior tocalling 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.
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 description of the last connection error
- mysqli_close() - Closes a previously opened database connection
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User Contributed Notes 13 notes
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28
fugyl13 at gmail dot com ¶
10 years ago
That's because since Windows 7, the hosts file doesn't come with a preconfigured So, if you notice a long connection creation, try "127.0.0.1" instead.Note that on all >=Windows 7 Servers, a host name "localhost" will create a very expensive lookup (~1 Second).
127.0.0.1 localhost
anymore
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29
andres at 21brains dot com ¶
10 years ago
We had a hard time figuring out what was going on since we were using mb_detect_encoding and it said everything was UTF-8, but of course the display was wrong. If we used iconv from ISO-8859-1 to UTF-8 the strings looked fine, even though everything in the database had the right collation. So in the end, it was the connection that was the filter and although the notes for this function mention default charsets, it almost reads as a sidenote instead of a central issue when dealing with UTF and PHP/MySQL.Please do use set_charset("utf8") after establishing the connection if you want to avoid weird string issues. I do not know why the documentation does not warn you about this kind of stuff.
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6
php at haravikk dot me ¶
6 years ago
What this means is that if you are hosting multiple applications, each with its own database user (as is good practice) then you will end up multiplying the number of connections that PHP may hold open. For example, if you have PHP configured with a maximum of eight worker processes, and you regularly use four different database users, then your MySQL server will need to accept at LEAST a maximum of 32 connections, or else it will run out. However, if you would like to minimise the number of connections, what you can do is instead is to open the connection using a "guest" user (with no privileges except logging in) and then use ->change_user() to switch to a more privileged user, before switching back to the guest when you're done. Since all of the connections would therefore belong to the guest user, PHP should only maintain one per worker process.Just wanted to add a note for anyone looking to use the MySQLi persistent connections feature; it's important to note that PHP opens and retains one connection per database user per process.
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8
chris at ocproducts dot com ¶
7 years ago
There is a caveat. If the host is 'localhost' then the port is ignored, whether you use a port parameter or the implicit syntax I mentioned above. This is because 'localhost' will make it use unix sockets rather than TCP/IP.There's a separate port parameter, unlike mysql_connect. However, using host:port on the host parameter does actually work.
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6
paul at mtnlist dot com ¶
11 years ago
Using 127.0.0.1 will work. Apparently, if you specify the host as "localhost", the constructor ignores the port specified as an argument to the constructor.If you want to connect via an alternate port (other than 3306), as you might when using an ssh tunnel to another host, using "localhost" as the hostname will not work.
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arnold at nijboer dot it ¶
1 year ago
the mysqli construct looks at the Master PHP.ini values.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")
)
if you're using a local ini overwrite of some sort add the ini_get to you're php script:
$mysqli = new mysqli(ini_get("mysqli.default_host"),ini_get("mysqli.default_user"),ini_get("mysqli.default_pw"))
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PaulieG ¶
8 years ago
To work around this, use 'null'.It should be noted that on PHP 7 (v7.0.2 at least), passing the empty string '' for the Port argument while connecting to 'localhost' will prevent the connection from being successful altogether.
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-2
Anonymous ¶
14 years ago
<?phpIf you get an error like
Can't connect to MySQL server on 'localhost' (10061)
and you use named pipes/socket connections (or aren't sure how you installed the MySQL server) try the following connect command:
mysqli_connect('.', $user_name, $password, $database_name, null, 'mysql');
?>
The '.' as hostname is absolutely necessary when using named pipes. 'localhost' won't work. 'mysql' is the standard name for the pipe/socket.
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Ben ¶
9 years ago
The config file itself is something like this: The following code fragment (in OO mysql_i format) $sqlconf='/var/private/my.cnf';A far more secure and language independent way of connecting to mysql is to use the READ_DEFAULT_FILE options. This passes the workload over to the mysql library, which allows for the configuration file itself to be outside of the scope of the language.
[client]
user=user_u
password=user_password
host=dbhost
port=3306
database=the_database
default-character-set=utf8
$sql = new mysqli;
$sql->init();
$sql->options(MYSQLI_READ_DEFAULT_FILE,$sqlconf);
$sql->real_connect();
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-6
linguafranca2003 at yahoo dot com ¶
9 years ago
GRANT USAGE ON *.* TO 'myuser'@'localhost' IDENTIFIED BY PASSWORD 'mypassword'; <?php if ( SQLSTATE: 00000 So, life is good — you're connected to the database and executing mysqli methods. Except, life isn't good, because you aren't actually using database_b because myuser doesn't have any privileges on it. You won't catch this until you try to perform a later operation, when you'll get an error, "MYSQL Error: No database selected", and find yourself scratching your head and thinking "what do you mean, of course I have a database selected; I selected one when I called the constructor". As a result, you may want to perform an additional check after connecting to mysql, to confirm that you're actually connected not just to the mysql server, but to the actual database: <?php if (mysqli can succeed in surprising ways, depending on the privileges granted to the user. For example,
GRANT ALL PRIVILEGES ON `database_a`.* TO 'myuser'@'localhost';
CREATE DATABASE database_b;
$db = new mysqli('localhost', 'myuser', 'mypassword', 'database_b');
die('Connect Error (' . $db->connect_errno . ') '
. $mysqli->connect_error);
}printf("SQLSTATE: %s\n", $this->db->sqlstate);
printf("Warning Count: %s\n", $db->warning_count);
$db->close();
?>
Will output:
Warning Count: 0
$db = new mysqli('localhost', 'myuser', 'mypassword', 'database_b');
die('Connect Error (' . $db->connect_errno . ') '
. $mysqli->connect_error);
} elseif ($result = $db->query("SELECT DATABASE()")) {
$row = $result->fetch_row();
if ($row[0] != 'database_b') {
//oops! We're connected to mysql, but not to database_b
}
}
?>
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-7
webmaster at aryes dot fr ¶
9 years ago
That gallery CMS was unable to connect to MySQL and left only a warning message about it. We tried to revert back to PHP 5.5, the CMS worked again. Then we switched back to 5.6.6 and changed those lines : $dbname = null; $mysqli = new mysqli($host, $user, $password, $dbname, $port, $socket); to $dbname = ''; // Use an empty string, not null $mysqli = new mysqli($host, $user, $password, $dbname, $port, $socket); It worked! So if you made the same mistake, using null where the manual invites to use an empty string, you should consider correcting your code.A friend of mine encountered a sudden bug with CMS Piwigo. I discovered that :
- He had a hosting rule to use PHP 5.6.
- The hoster uses 5.6.6, verified using phpinfo();.
- The CMS declared a database name parameter as null.
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-4
powtac at gmx de ¶
6 years ago
Be careful, mysqli_connect() does not return a resource ! It returns an instance of the mysqli class (http://php.net/manual/class.mysqli.php) The old mysql_connect() function did return a resource.
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-15
oleg at mastak dot fi ¶
11 years ago
Named pipes support for Windows was added in PHP version 5.4.0. Hopefully that will save you some time.If you want to connect to local named pipe on windows and you get error "php_network_getaddresses: getaddrinfo failed: No such host is known. ", even if you using using "." as host, please check your if you are using mysqlnd driver: If this is true, then probably you need to update to version 5.4 of php:
@ http://php.net/manual/en/mysqlnd.overview.php
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