Check whether the username is written in php that already exists in mysql.

There are many methods to check whether the user name already exists in mysql. The following describes how to use php to write the registration system. if you want to check whether the user name exists, php can write as follows:

The code is as follows:

$ Username = $ _ REQUEST ['username'];
$ Password = $ _ REQUEST ['password'];
Echo"
Excute the insertUserInfo ";
$ Con = mysqli_connect ("localhost", "root", "", "my_db ");
$ SQL = "SELECT * FROM user WHERE username = '$ username '";

Ho"
This username aready exists ";} else {$ SQL =" INSERT INTO user (username, password) VALUES ('$ username',' $ password') "; if (! Mysqli_query ($ con, $ SQL) {echo"
Error ". mysqli_error ($ con);} else {echo"
One record added ";}}

Do not use:

The code is as follows:

Mysql_num_rows ($ result)
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