简单更新php中的两个字段会出错

Question

I am trying to update some fields in a mysql database from php. This always gives me error, and I don't know why. Could you have a quick look?

         $sqlupdate_ = "UPDATE $db SET city=$city, country=$country WHERE  userIP=$ip;";
              $sqlupdate = mysql_query($sqlupdate_);
              echo $sqlupdate_;

 if($sqlupdate){

      //The query returned true - now do whatever you like here.
      echo 'success';

 }else{

      //The query returned false - you might want to put some sort of error reporting here. Even logging the error to a text file is fine.
      echo "error: ";

 }

Answer 1

First of all:, use mysqli or PDO since mysql functions are depracated.

Second: avoid sql injections with escape your strings.

I think, your problem is that, your city, country and ip are varchars not integers, so you need to add quotes around them, and you want to update your table not your database.

Try to echoes your query and run directly in mysql.

$sqlupdate_ = "UPDATE " . mysqli_real_escape_string($link, $db). " SET city= '" .mysqli_real_escape_string($link, $city) ."', country='".mysqli_real_escape_string($link, $country)."' WHERE  userIP='".mysqli_real_escape_string($link, $ip)."'";