(PHP 5)
mysqli::__construct -- mysqli_connect — Open a new connection to the MySQL server
面向对象风格
$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")
]]]]]] )过程化风格
$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")
]]]]]] )Opens a connection to the MySQL Server running on.
host
Can be either a host name or an IP address. Passing the NULL value
or the string "localhost" to this parameter, the local host is
assumed. When possible, pipes will be used instead of the TCP/IP
protocol.
Prepending host by p: opens a persistent connection. mysqli_change_user() is automatically called on connections opened from the connection pool.
username
The MySQL user name.
passwd
If not provided or NULL, the MySQL server will attempt to authenticate
the user against those user records which have no password only. This
allows one username to be used with different permissions (depending
on if a password as provided or not).
dbname
If provided will specify the default database to be used when performing queries.
port
Specifies the port number to attempt to connect to the MySQL server.
socket
Specifies the socket or named pipe that should be used.
Note:
Specifying the
socketparameter 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 thehostparameter.
Returns an object which represents the connection to a MySQL Server.
| 版本 | 说明 |
|---|---|
| 5.3.0 | Added the ability of persistent connections. |
Example #1 mysqli::__construct() example
面向对象风格
<?php
$mysqli = new mysqli('localhost', 'my_user', 'my_password', 'my_db');
/*
* This is the "official" OO way to do it,
* BUT $connect_error was broken until PHP 5.2.9 and 5.3.0.
*/
if ($mysqli->connect_error) {
die('Connect Error (' . $mysqli->connect_errno . ') '
. $mysqli->connect_error);
}
/*
* Use this instead of $connect_error if you need to ensure
* compatibility with PHP versions prior to 5.2.9 and 5.3.0.
*/
if (mysqli_connect_error()) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Success... ' . $mysqli->host_info . "\n";
$mysqli->close();
?>
面向对象风格 when extending mysqli class
<?php
class foo_mysqli extends mysqli {
public function __construct($host, $user, $pass, $db) {
parent::__construct($host, $user, $pass, $db);
if (mysqli_connect_error()) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
}
}
$db = new foo_mysqli('localhost', 'my_user', 'my_password', 'my_db');
echo 'Success... ' . $db->host_info . "\n";
$db->close();
?>
过程化风格
<?php
$link = mysqli_connect('localhost', 'my_user', 'my_password', 'my_db');
if (!$link) {
die('Connect Error (' . mysqli_connect_errno() . ') '
. mysqli_connect_error());
}
echo 'Success... ' . mysqli_get_host_info($link) . "\n";
mysqli_close($link);
?>
以上例程会输出：
Success... MySQL host info: localhost via TCP/IP
Note:
MySQLnd always assumes the server default charset. This charset is sent during connection hand-shake/authentication, which mysqlnd will use.
Libmysql uses the default charset set in the my.cnf or by an explicit call to mysqli_options() prior to calling mysqli_real_connect(), but after mysqli_init().
Note:
OO syntax only: If a connection fails an object is still returned. To check if the connection failed then 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 the SYSTEMROOT environment variable won't be available and PHP will have problems loading Winsock.