PHP operates mysqli database connection

* mysqli database connection

* Steps:

* 1. Create connection parameters

* 2. Call the connection function and return the connection resource

* 3. Determine whether the connection is successful

* 4. Select the database

* 5. Set the default character set

* Functions used

* 1 . mysqli_connect($host,$user,$pass)

* 2. mysqli_connect_errno($db)

* 3. mysqli_connect_error($db)

* 4. mysqli_select_db ($dbName)

* 5. mysqli_set_charset('utf8')

//1. Create connection parameters

//Create connection parameters: Because the connection parameters are not frequent changes, so it is recommended to use the constant

define ('DB_HOST', 'localhost');
define ('DB_USER', 'root');
define ('DB_PASS', 'root');
define ('DB_NAME', 'php');
define ('DB_CHAR', 'utf8');

//2. Call the connection function, the mysqli object will be returned if successful, and false will be returned if failed

$db = @mysqli_connect(DB_HOST, DB_USER, DB_PASS);
var_dump($db);die();

//3. Is the test connection successful?

//Failed connection will definitely return an error number. You can judge based on the number, or you can use whether $db is false to judge.

if (mysqli_connect_errno($db)) {
    exit('连接失败'.mysqli_connect_error($db));
}
echo &#39;<h1>连接成功</h1>&#39;;

//4. Select the database to be operated

mysqli_select_db($db, DB_NAME);

/ /5. Set the default character set

mysqli_set_charset($db, DB_CHAR);