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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