Steps to connect to database in php

This article mainly introduces how to connect to the database in PHP. I hope it helps everyone. Let’s get straight to the content without saying much.

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##PHP Connect to Database

1. Connect database function

　

mysqli_connect(hostname, username, password) The return value is one of our connections The object returns false if the connection fails

2. Judgment error function

　

mysqli_connect_error(connection object) Error message Return error message

　

mysqli_connect_errno(connection object) Error number 0 means the connection is successful and there is no error

3. Select database function

　

mysqli_select_db(connection Object, the database name to be selected); Returns true if the selection is successful, otherwise returns false

4. Select the character set

　

mysqli_set_charset(Connection object , the character set to be selected);If the selection is successful, return true, otherwise return false

5. Prepare the sql statement

　Written by yourself

6. Send sql statement

　

mysqli_query (connection object, sql statement to be sent); Get an object successfully, return false on failure

7. Processing the result set

7.1 Get the number of entries

a) mysqli_num_rows (the object that successfully sent SQL) is used to get the number of records obtained by the query. It can only be used in select statements

b) mysqli_affected_rows (connection object) The number of affected rows in the previous mysql operation. Only the INSERT UPDATE DELETE operation uses the return value 1 to successfully insert the number of rows -1. Execution failed

　7.2 Obtain query results Contents of the set

　　

mysqli_fetch_array(Send object) Return the query results in the form of a mixed array and return one item at a time

　　

mysqli_fetch_row(Send object) Return the results of the query in the form of an index array and return one item at a time

　

mysqli_fetch_assoc (sending object) Return the results of the query in the form of an associative array and return one item at a time

　7.3 When adding the operation, we can get the last inserted id

　　

mysqli_insert_id (connection object) Return the last inserted id

8. Close the database

mysqli_close(connection object)

// 1.连接数据库
// 2.判断错误
// 3.选择数据库
// 4.选择字符集
// 5.准备sql语句
// 6.发送sql语句
// 7.处理结果集
// 8.关闭数据库

//1.连接数据库
//mysqli_connect('主机名','用户名','密码');
$link=@mysqli_connect('localhost','root','123456');
//var_dump($link);

//2.判断错误
//mysqli_connect_error(连接对象) 错误信息
//mysqli_connect_errno(连接对象)   错误号
// echo mysqli_connect_errno($link);
// echo mysqli_connect_error($link);
if(mysqli_connect_errno($link)){
　　echo mysqli_connect_error($link);exit;
//echo '错误了 重新连接';exit;
}

//3.选择数据库
mysqli_select_db($link,'ss21');

//4.选择字符集
mysqli_set_charset($link,'utf8');

//5.准备sql语句
$sql="SELECT id,name,sex,age,city FROM info";
//$sql="INSERT INTO info(name) VALUES(NULL)";

//6.发送sql语句
$result = mysqli_query($link,$sql);

//7.处理结果集
echo mysqli_num_rows($result);
//echo mysqli_affected_rows($link);

//8.关闭数据库
mysqli_close($link);

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