This article mainly introduces PHP to use the mysqli extension to connect to the MySQL database. Friends who need it can refer to it

1. Object-oriented usage

$db = new mysqli('localhost', 'root', '123456', 'dbname');

If the database is not specified when establishing the connection, select the database to use and switch to use Database

$db->select_db('dbname');
  
$query = "SELECT * FROM user WHERE uid=4";
  
$result = $db->query($query);
  
$result_num = $result->num_rows;
  
$row = $result->fetch_assoc();  //返回一個關(guān)聯(lián)數(shù)組，可以通過$row['uid']的方式取得值
  
$row = $result->fetch_row();  //返回一個列舉數(shù)組，可以通過$row[0]的方式取得值
  
$row = $result->fetch_array();  //返回一個混合數(shù)組，可以通過$row['uid']和$row[0]兩種方式取得值
  
$row = $result->fetch_object();  //返回一個對象，可以通過$row->uid的方式取得值
  
$result->free();  //釋放結(jié)果集
  
$db->close();  //關(guān)閉一個數(shù)據(jù)庫連接，這不是必要的，因為腳本執(zhí)行完畢時會自動關(guān)閉連接

When performing INSERT, UPDATE, and DELETE operations, use $db->affected_rows to view the number of affected rows

2. Process-oriented usage

$db = mysqli_connect('localhost', 'root', '123456', 'dbname');

If the database is not specified when establishing a connection, the database will be selected. Database, switch the database used

mysqli_select_db($db, 'dbname');

Query the database

$query = "SELECT * FROM user WHERE uid=4";
  
$result = mysqli_query($db, $query);
  
$result_num = mysqli_num_rows($result);

Return one row of results

$row = mysqli_fetch_assoc($result);  //返回一個關(guān)聯(lián)數(shù)組，可以通過$row['uid']的方式取得值
  
$row = mysqli_fetch_row($result);  //返回一個列舉數(shù)組，可以通過$row[0]的方式取得值
  
$row = mysqli_fetch_array($result);  //返回一個混合數(shù)組，可以通過$row['uid']和$row[0]兩種方式取得值
  
$row = mysqli_fetch_object($result);  //返回一個對象，可以通過$row->uid的方式取得值

Disconnect the database

mysqli_free_result($result);  //釋放結(jié)果集
  
mysqli_close($db);  //關(guān)閉一個數(shù)據(jù)庫連接，這不是必要的，因為腳本執(zhí)行完畢時會自動關(guān)閉連接

When performing INSERT, UPDATE, DELETE operations, use mysqli_affected_rows() to view the number of affected rows