mysqli::__construct

mysqli::connect

mysqli_connect

(PHP 5, PHP 7, PHP 8)

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

Опис

Об'єктно-орієнтований стиль

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

Процедурний стиль

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.

Параметри

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.

Зауваження:
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.

Значення, що повертаються

mysqli_connect() returns an object which represents the connection to a MySQL Server, або false в разі помилки.

mysqli::connect() returns true on success або false в разі помилки. Prior to PHP 8.1.0, returns null on success.

Помилки/виключення

Якщо увімкнені звіти про помилки mysqli (MYSQLI_REPORT_ERROR) і запитана операція не виконалась, буде виведено попередження, але якщо встановлено режим MYSQLI_REPORT_STRICT, буде викинуто виключення mysqli_sql_exception.

Журнал змін

Версія	Опис
8.1.0	mysqli::connect() now returns `true` instead of `null` on success.
7.4.0	All parameters are now nullable.

Приклади

Приклад #1 mysqli::__construct() example

Об'єктно-орієнтований стиль

<?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);

Процедурний стиль

<?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));

Подані вище приклади виведуть щось схоже на:

Success... localhost via TCP/IP

Приклад #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');

Приклад #3 Manual error handling

If error reporting is disabled, the developer is responsible for checking and handling failures

Об'єктно-орієнтований стиль

<?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);
}

Процедурний стиль

<?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));
}

Примітки

Зауваження:
MySQLnd завжди використовує стандартне кодування символів на сервері. Це кодування надсилається на етапі з'єднання/автентифікації, які використовує mysqlnd.
Libmysqlclient використовує кодування символів, вказане у файлі my.cnf, або явним викликом функції mysqli_options() перед викликом mysqli_real_connect(), але після mysqli_init().

Зауваження:
Об'єктно-орієнтований стиль 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.

Зауваження:
If it is necessary to set options, such as the connection timeout, mysqli_real_connect() must be used instead.

Зауваження:
Calling the constructor with no parameters is the same as calling mysqli_init().

Зауваження:
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.

Прогляньте також

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 10 notes

down

fugyl13 at gmail dot com ¶

10 years ago

Note that on all >=Windows 7 Servers, a host name "localhost" will create a very expensive lookup (~1 Second). 

That's because since Windows 7, the hosts file doesn't come with a preconfigured
127.0.0.1 localhost
anymore

So, if you notice a long connection creation, try "127.0.0.1" instead.

down

andres at 21brains dot com ¶

10 years ago

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.

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.

down

php at haravikk dot me ¶

7 years ago

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.

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.

down

chris at ocproducts dot com ¶

7 years ago

There's a separate port parameter, unlike mysql_connect. However, using host:port on the host parameter does actually work.

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.

down

paul at mtnlist dot com ¶

11 years ago

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. 

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.

down

-1

arnold at nijboer dot it ¶

1 year ago

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")
)

the mysqli construct looks at the Master PHP.ini values.
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"))

down

PaulieG ¶

8 years ago

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.

To work around this, use 'null'.

down

-2

Anonymous ¶

15 years ago

If 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:



<?php

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.

down

-5

Ben ¶

9 years ago

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.

The config file itself is something like this:
[client]
user=user_u
password=user_password
host=dbhost
port=3306
database=the_database
default-character-set=utf8

The following code fragment (in OO mysql_i format)

$sqlconf='/var/private/my.cnf';
$sql = new mysqli;
$sql->init();
$sql->options(MYSQLI_READ_DEFAULT_FILE,$sqlconf);
$sql->real_connect();

down

-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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