Mysqli several ways to connect to a database

Configuration information:

Server: localhost

MySQL User name: root

MySQL Password: hanxin

Database name: admin

Mysqli uses object-oriented thinking to program, that is, to manipulate the database by mysqli the properties and methods of the object.

(1)
1. Establish a connection to MySQL data
$mysqli = new mysqli (' localhost ', ' root ', ' hanxin ');
2. Open the specified database
$mysqli->select_db (' admin ');

(2)
$mysqli =new mysqli ();
$mysqli->connect (' 127.0.0.1 ', ' root ', ' hanxin ');

$mysqli->select_db (' admin ');

(3)
$mysqli =new mysqli ();
$mysqli->connect (' 127.0.0.1 ', ' root ', ' hanxin ', ' admin ');
(4)
Open the specified database while establishing the connection
[Email protected] mysqli (' localhost ', ' root ', ' hanxin ', admin ');
There are errors but do not let the display in front plus @

$mysqli->connect_errno: Get the error number of the connection generated
$mysqli->connect_error: Get the error message generated by the connection

if ($mysqli->connect_error) {
Die (' Connect Error: '. $mysqli->connect_error);
}

Mysqli several ways to connect to a database