PHP connection to MySQL database code

CopyCodeThe Code is as follows: <? PHP
Mysql_connect ("localhost", "root", "1981427") // connect to the server on localhost. The username is root.
?> Copy codeThe Code is as follows: <? PHP
@ Mysql_connect ("localhost", "root", "1981427 ")
Or die ("database server connection failed ");
?> Copy codeThe Code is as follows: <? PHP
@ Mysql_connect ("localhost", "root", "1981427") // You must connect to the database server before selecting a database.
Or die ("database server connection failed ");
@ Mysql_select_db ("test") // select the database mydb
Or die ("the database does not exist or is unavailable ");
?>