MySql Unknown列在哪里

Question

I am a beginner and try to have a very simple messaging system. every thing is managed via the ID's of the users..

So if someone types the username of a person i have to convert it into the person's id:

$res_name = $_POST["res_name"];
    $res_id = userToId($res_name);

This function looks like this:

function userToId($username) {
    $data = array();
    $func_get_args = func_get_args();

    if($func_num_args = 1)
    {
    $res = mysql_query("SELECT id FROM `z_network_users` WHERE `username` = `$username`") or die(mysql_error());
    $data = mysql_fetch_assoc($res);
    }
    return $data['id'];
}

it doesn't work, in fact it can't find a username even if it's existing..

the error is for example:

Unknown column 'testperson' in 'where clause'

the user exists, hope you can help me :) ps: I know I shouldn't use mysql_* but i haven' learned the better version.. ;)

Answer 1

When using backticks around your variable then it will be considered as column

thats why you got that error Unknown column 'testperson' in 'where clause'

you should use this (you should escape your variable to prevent sql injection)

 $username = mysql_real_escape_string($username);
 $res = mysql_query("SELECT id FROM `z_network_users` 
        WHERE `username` = '$username' ") or die(mysql_error());

or this

 $username = mysql_real_escape_string($username);
 $res = mysql_query("SELECT id FROM `z_network_users` 
        WHERE `username` = '".$username."' ") or die(mysql_error());

try that function:

 function userToId($username) {

   $func_get_args = func_get_args();
    $username = mysql_real_escape_string($username);
   if($func_num_args == 1)
{
   $res = mysql_query("SELECT id FROM `z_network_users` WHERE `username` = '$username' ") or die(mysql_error());
   $row = mysql_fetch_assoc($res);

}
  return $row['id'];
}