International PHP Conference 2015

mysqli::__construct

mysqli_connect

(PHP 5)

mysqli::__construct -- mysqli_connectOuvre une connexion à un serveur MySQL

Description

Style orienté objet

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") ]]]]]] )

Style procédural

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") ]]]]]] )

Ouvre une connexion sur un serveur MySQL.

Liste de paramètres

host

Peut être un nom d'hôte ou une adresse IP. Si vous passez la valeur NULL ou la chaîne "localhost" à ce paramètre, l'hôte local est sous-entendu. Lorsque c'est possible, les sockets seront utilisées au lieu du protocole TCP/IP.

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.

passwd

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 que l'on fournit le mot de passe ou non).

dbname

Si fourni, spécifiera la base de données par défaut à utiliser lors de l'exécution de requêtes.

port

Spécifie le numéro du port pour la connexion au serveur MySQL.

socket

Spécifie le socket ou le nom du tunnel à utiliser.

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 host.

Valeurs de retour

Retourne un objet qui représente la connexion au serveur MySQL.

Historique

Version Description
5.3.0 Ajout des connexions persistantes.

Exemples

Exemple #1 Exemple avec mysqli::__construct()

Style orienté objet

<?php
$mysqli 
= new mysqli('localhost''my_user''my_password''my_db');

/*
 * Ceci est le style POO "officiel"
 * MAIS $connect_error était erroné jusqu'en PHP 5.2.9 et 5.3.0.
 */
if ($mysqli->connect_error) {
    die(
'Erreur de connexion (' $mysqli->connect_errno ') '
            
$mysqli->connect_error);
}

/*
 * Utilisez cette syntaxe de $connect_error si vous devez assurer
 * la compatibilité avec les versions de PHP avant 5.2.9 et 5.3.0.
 */
if (mysqli_connect_error()) {
    die(
'Erreur de connexion (' mysqli_connect_errno() . ') '
            
mysqli_connect_error());
}

echo 
'Succès... ' $mysqli->host_info "\n";

$mysqli->close();
?>

Style orienté objet 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(
'Erreur de connexion (' mysqli_connect_errno() . ') '
                    
mysqli_connect_error());
        }
    }
}

$db = new foo_mysqli('localhost''my_user''my_password''my_db');

echo 
'Succès... ' $db->host_info "\n";

$db->close();
?>

Style procédural

<?php
$link 
mysqli_connect('localhost''my_user''my_password''my_db');

if (!
$link) {
    die(
'Erreur de connexion (' mysqli_connect_errno() . ') '
            
mysqli_connect_error());
}

echo 
'Succès... ' mysqli_get_host_info($link) . "\n";

mysqli_close($link);
?>

Les exemples ci-dessus vont afficher :

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

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:

Uniquement pour la syntaxe orientée objet : pour vérifier si la connexion a échoué, utilisez 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

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User Contributed Notes 8 notes

up
10
andres at 21brains dot com
1 year 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.
up
7
fugyl13 at gmail dot com
1 year 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.
up
3
paul at mtnlist dot com
2 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.
up
2
Anonymous
5 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.
up
0
webmaster at aryes dot fr
1 month 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.
up
-1
Ben
5 months 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();
up
-2
linguafranca2003 at yahoo dot com
9 months 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
       
}
}
?>
up
-2
oleg at mastak dot fi
2 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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