How to check whether the username already exists in mysql in php_PHP tutorial

When writing the registration system, if you want to check whether the user name exists, PHP can write like this:

Copy code 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"; } }

It is recommended not to use:

Copy code The code is as follows:

mysql_num_rows($result)
lt;pre name="code" class ="html">

http://www.bkjia.com/PHPjc/718603.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/718603.htmlTechArticleWhen writing the registration system, if you want to check whether the user name exists, PHP can write like this: Copy the code as follows: $username=$_REQUEST['username']; $password=$_REQUEST['password']; ech...