检查数据库中是否存在用户名

Question

如果用户名存在，试图阻止用户注册。 这是我的代码：

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 

我已经尝试了很多其他的东西让它工作，但由于某种原因我的代码不喜欢我......

Answer 1

将mysql_num_rows更改为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
            {  //

在查询中使用它之前，请使用bind param或proplerly转义您的值。

Answer 2

更改..

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

至

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

你在$ sql中指定了查询并在$ query中执行...也得到输入为...

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

出于安全原因......

Answer 3

将您的查询更改为：

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

$result=mysql_query($sql);

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

Answer 4

mysql_num_rows从PHP 5.5.0不推荐使用，将来会被删除

所以使用替代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

你的$query变量必须是mysqli_query中的第二个参数，而不是你使用$sql 。 所以用mysqli_query()函数中的$ query替换$sql并使用mysqli而不是mysql_num_rows()