mysqli::__construct

mysqli::connect

mysqli_connect

(PHP 5, PHP 7, PHP 8)

mysqli::__construct -- mysqli::connect -- mysqli_connect — Ouvre une connexion à un serveur MySQL

Description

Style orienté objet

public mysqli::__construct(
    ?string $hostname = null,
    ?string $username = null,
    ?string $password = null,
    ?string $database = null,
    ?int $port = null,
    ?string $socket = null
)

public mysqli::connect(
    ?string $hostname = null,
    ?string $username = null,
    ?string $password = null,
    ?string $database = null,
    ?int $port = null,
    ?string $socket = null
): bool

Style procédural

mysqli_connect(
    ?string $hostname = null,
    ?string $username = null,
    ?string $password = null,
    ?string $database = null,
    ?int $port = null,
    ?string $socket = null
): mysqli|false

Ouvre une connexion au serveur MySQL.

Liste de paramètres

hostname

Peut être un nom d'hôte ou une adresse IP. Lorsqu'on passe null, la valeur est récupérée depuis mysqli.default_host. Si possible, les pipes seront utilisé à la place du protocole TCP/IP. Le protocol TCP/IP est utilisé si un nom d'hôte et numéro de port sont fournis ensemble, par exemple localhost:3308.

Préfixer l'hôte par p: ouvre une connexion persistante mysqli_change_user() est automatiquement appelé sur les connexions qui sont utilisées dans le pool de connexions.

username

Le nom d'utilisateur MySQL ou null pour supposer le nom d'utilisateur en fonction de l'option ini mysqli.default_user.

password

Si le mot de passe n'est pas indiqué (la valeur null est passée), le serveur MySQL essaiera d'identifier l'utilisateur en étudiant que les enregistrements où les utilisateurs n'ont pas de mot de passe. Cela permet à un utilisateur de jouir de plusieurs permissions (selon qu'un mot de passe est fournit ou non).

database

La base de données par défaut à utiliser lors de l'exécution de requêtes ou null.

port

Le numéro de port auquel tenter de se connecter au serveur MySQL ou null pour supposer le port en fonction de l'option ini mysqli.default_port.

socket

Le socket ou le pipe nommé qui doit être utilisé, ou null pour supposer le socket en fonction de l'option ini mysqli.default_socket.

Note:
Spécifier le paramètre socket ne déterminera pas explicitement le type de connexion qui sera utilisé lors de la connexion au serveur MySQL. Cela est déterminé par le paramètre hostname.

Valeurs de retour

mysqli_connect() retourne un objet qui représente la connexion au serveur MySQL, ou false si une erreur survient.

mysqli::connect() renvoie true en cas de succès ou false si une erreur survient. Antérieur à PHP 8.1.0, renvoie null en cas de succès.

Erreurs / Exceptions

Si le rapport d'erreurs mysqli est activé (MYSQLI_REPORT_ERROR) et que l'opération demandée échoue, un avertissement est généré. Si, en plus, le mode est défini sur MYSQLI_REPORT_STRICT, une mysqli_sql_exception est lancée à la place.

Historique

Version	Description
8.1.0	mysqli::connect() retourne désormais `true` au lieu de `null` en cas de succès.
7.4.0	Tous les paramètres sont désormais nullable.

Exemples

Exemple #1 Exemple mysqli::__construct()

Style orienté objet

<?php
/* Vous devriez toujours activer le rapport d'erreur pour mysqli avant une tentative de connexion */
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
/* Définir le jeu de caractère désiré après avoir établie une connexion */
$mysqli->set_charset('utf8mb4');
printf("Success... %s\n", $mysqli->host_info);

Style procédural

<?php
/* Vous devriez toujours activer le rapport d'erreur pour mysqli avant une tentative de connexion */
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
/* Définir le jeu de caractère désiré après avoir établie une connexion */
mysqli_set_charset($mysqli, 'utf8mb4');
printf("Success... %s\n", mysqli_get_host_info($mysqli));

Les exemples ci-dessus vont afficher quelque chose de similaire à :

Success... localhost via TCP/IP

Exemple #2 Étendre la classe mysqli

<?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');

Exemple #3 Gestion d'erreur manuelle

Si le rapport d'erreur est désactivé, le développeur est responsable pour vérifier et gérer les échecs

Style orienté objet

<?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);
}
/* Définir le jeu de caractère désiré après avoir établie une connexion */
$mysqli->set_charset('utf8mb4');
if ($mysqli->errno) {
    throw new RuntimeException('mysqli error: ' . $mysqli->error);
}

Style procédural

<?php
error_reporting(0);
mysqli_report(MYSQLI_REPORT_OFF);
$mysqli = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (mysqli_connect_errno()) {
    throw new RuntimeException('mysqli connection error: ' . mysqli_connect_error());
}
/* Définir le jeu de caractère désiré après avoir établie une connexion */
mysqli_set_charset($mysqli, 'utf8mb4');
if (mysqli_errno($mysqli)) {
    throw new RuntimeException('mysqli error: ' . mysqli_error($mysqli));
}

Notes

Note:
MySQLnd s'occupe toujours du jeu de caractères par défaut du serveur. Celui-ci est envoyé durant la négociation de la connexion ou l'authentification.
Libmysqlclient utilise le jeu de caractères par défaut de my.cnf ou via par un appel à mysqli_options() avant mysqli_real_connect(), mais après mysqli_init().

Note:
Style orienté objet uniquement : si la connexion a échoué, un objet est quand même retourné. Pour vérifier si la connexion a échoué, utilisez soit la fonction mysqli_connect_error() ou la propriété mysqli->connect_error comme dans l'exemple ci-dessus.

Note:
S'il est nécessaire de configurer des options, telles que le délai de connexion, mysqli_real_connect() doit être utilisé.

Note:
Appeler le constructeur sans paramètre a le même effet qu'appeler mysqli_init().

Note:
L'erreur "Can't create TCP/IP socket (10106)" signifie à généralement que la directive de configuration variables_order ne contient pas le caractère E. Sous Windows, si l'environnement n'est pas copié, la variable d'environnement SYSTEMROOT ne sera pas disponible et PHP aura des soucis pour charger Winsock.

Voir aussi

mysqli_real_connect() - Ouvre une connexion à un serveur MySQL
mysqli_options() - Définit les options
mysqli_connect_errno() - Retourne le code d'erreur du dernier appel de connexion
mysqli_connect_error() - Retourne une description de la dernière erreur de connexion
mysqli_close() - Ferme une connexion

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User Contributed Notes 13 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.

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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.

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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.

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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.

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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.

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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'.

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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"))

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-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.

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-6

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();

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-6

linguafranca2003 at yahoo dot com ¶

9 years ago


mysqli can succeed in surprising ways, depending on the privileges granted to the user. For example,

GRANT USAGE ON *.* TO 'myuser'@'localhost' IDENTIFIED BY PASSWORD 'mypassword';
GRANT ALL PRIVILEGES ON `database_a`.* TO 'myuser'@'localhost';
CREATE DATABASE database_b;

<?php
$db = new mysqli('localhost', 'myuser', 'mypassword', 'database_b');

if ($db->connect_error) {
        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:

SQLSTATE: 00000 
Warning Count: 0

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
$db = new mysqli('localhost', 'myuser', 'mypassword', 'database_b');

if ($db->connect_error) {
        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


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.

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.

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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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-14

oleg at mastak dot fi ¶

11 years ago


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:

Named pipes support for Windows was added in PHP version 5.4.0.
@ http://php.net/manual/en/mysqlnd.overview.php 

Hopefully that will save you some time.

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