检查数据库中是否存在用户名

Question

pretty stuck on trying to prevent the user from registering if the username exists. Here is my code:

include('../connection.php');
//get all the names and values that have been posted.
    $username = $_POST['username'];   
    //check if username exists
    $sql = "SELECT * FROM tbl_Freelancers WHERE User_Username = '".$username."'";
    $result = mysqli_query($con,$query);
    if(mysql_num_rows($result)>=1)
       {
        echo"name already exists";
       }
     else
        {  // excecute insert query 

I have tried loads of other stuff to get it working but for some reason my code doesn't like me......

Answer 1

change mysql_num_rows to mysqli_num_rows

if(mysqli_num_rows($result)>=1)//You are mixing the mysql and mysqli, change this line of code
           {
            echo"name already exists";
           }
         else
            {  //

use bind param or proplerly escape your value, before using it in query.

Answer 2

change..

$sql = "SELECT * FROM tbl_Freelancers WHERE User_Username = '".$username."'";
    $result = mysqli_query($con,$query);

to

$sql = "SELECT * FROM tbl_Freelancers WHERE User_Username = '".$username."'";
    $result = mysqli_query($con,$sql);

you specified query in $sql and executing in $query... also get input as..

 $username = mysqli_real_escape_string($con, $_POST['username']);   

for security reasons...

Answer 3

alter your query to:

 $sql= "SELECT * FROM tbl_Freelancers WHERE User_Username = '$username'";

$result=mysql_query($sql);

if(mysql_num_rows($result)!=0)
       {
        echo"name already exists";
       }
     else
        {  
        // excecute insert query 
        }

Answer 4

mysql_num_rows is deprecated as of PHP 5.5.0 , and will be removed in the future

So use alternative mysqli_num_rows

Answer 5

try this

include('../connection.php');
 $username = $_POST['username'];   
  $sql = "SELECT * FROM tbl_Freelancers WHERE User_Username = '".$username."'";
    $result = mysql_query($sql);
    if(mysql_num_rows($result)!=0)
       {
        echo"name already exists";
       }
     else
        {
        echo ".........";
}   

Answer 6

your $query variable has to be a second argument in mysqli_query , instead you used $sql . so replace $sql with $query in mysqli_query() function and use mysqli instead of mysql_num_rows()