PHP: Hypertext Preprocessor (original) (raw)

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

Description

Object-oriented style

Parameters

hostname

Can be either a host name or an IP address. When passing [null](reserved.constants.php#constant.null), the value is retrieved frommysqli.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](reserved.constants.php#constant.null) to assume the username based on themysqli.default_user ini option.

password

The MySQL password or [null](reserved.constants.php#constant.null) to assume the password based on themysqli.default_pw ini option.

database

The default database to be used when performing queries or [null](reserved.constants.php#constant.null).

port

The port number to attempt to connect to the MySQL server or [null](reserved.constants.php#constant.null) to assume the port based on themysqli.default_port ini option.

socket

The socket or named pipe that should be used or [null](reserved.constants.php#constant.null) to assume the socket based on themysqli.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 the hostname parameter.

Return Values

mysqli::__construct() always returns an object which represents the connection to a MySQL Server, regardless of it being successful or not.

mysqli_connect() returns an object which represents the connection to a MySQL Server, or [false](reserved.constants.php#constant.false) on failure.

mysqli::connect() returns [true](reserved.constants.php#constant.true) on success or [false](reserved.constants.php#constant.false) on failure. Prior to PHP 8.1.0, returns [null](reserved.constants.php#constant.null) on success.

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 */ <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>m</mi><mi>y</mi><mi>s</mi><mi>q</mi><mi>l</mi><mi>i</mi><mo>−</mo><mo>></mo><mi>s</mi><mi>e</mi><msub><mi>t</mi><mi>c</mi></msub><mi>h</mi><mi>a</mi><mi>r</mi><mi>s</mi><mi>e</mi><mi>t</mi><msup><mo stretchy="false">(</mo><mo mathvariant="normal" lspace="0em" rspace="0em">′</mo></msup><mi>u</mi><mi>t</mi><mi>f</mi><mn>8</mn><mi>m</mi><mi>b</mi><msup><mn>4</mn><mo mathvariant="normal" lspace="0em" rspace="0em">′</mo></msup><mo stretchy="false">)</mo><mo separator="true">;</mo><mi>p</mi><mi>r</mi><mi>i</mi><mi>n</mi><mi>t</mi><mi>f</mi><mo stretchy="false">(</mo><mi mathvariant="normal">"</mi><mi>S</mi><mi>u</mi><mi>c</mi><mi>c</mi><mi>e</mi><mi>s</mi><mi>s</mi><mi mathvariant="normal">.</mi><mi mathvariant="normal">.</mi><mi mathvariant="normal">.</mi></mrow><annotation encoding="application/x-tex">mysqli->set_charset('utf8mb4');printf("Success... %s\n", </annotation></semantics></math>mysqli−>setcharset(′utf8mb4′);printf("Success...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 output something similar to:

Success... localhost via TCP/IP

Example #2 Extending mysqli class

<?phpclass FooMysqli extends mysqli { public function __construct($host, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>u</mi><mi>s</mi><mi>e</mi><mi>r</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">user, </annotation></semantics></math>user,pass, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>d</mi><mi>b</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">db, </annotation></semantics></math>db,port, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>s</mi><mi>o</mi><mi>c</mi><mi>k</mi><mi>e</mi><mi>t</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">socket, </annotation></semantics></math>socket,charset) { mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT); parent::__construct($host, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>u</mi><mi>s</mi><mi>e</mi><mi>r</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">user, </annotation></semantics></math>user,pass, <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>d</mi><mi>b</mi><mo separator="true">,</mo></mrow><annotation encoding="application/x-tex">db, </annotation></semantics></math>db,port, $socket); <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><mi>t</mi><mi>h</mi><mi>i</mi><mi>s</mi><mo>−</mo><mo>></mo><mi>s</mi><mi>e</mi><msub><mi>t</mi><mi>c</mi></msub><mi>h</mi><mi>a</mi><mi>r</mi><mi>s</mi><mi>e</mi><mi>t</mi><mo stretchy="false">(</mo></mrow><annotation encoding="application/x-tex">this->set_charset(</annotation></semantics></math>this−>setcharset(charset); } }$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

`<?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);
}`

Procedural style

`<?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));
}`

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 themy.cnf or by an explicit call to mysqli_options() prior to calling 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 callingmysqli_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.

Found A Problem?

fugyl13 at gmail dot com ¶

11 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.

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.

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.

chris at ocproducts dot com ¶

8 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.

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.

PHP: Hypertext Preprocessor (original) (raw)

mysqli::__construct

mysqli::connect

mysqli_connect

Description

Parameters

Return Values

Changelog

Examples

Notes

See Also

Found A Problem?