MySql query syntax error despite everything being correct

Question

All the server details are put correctly, and the connection does happen properly, I cannot seem to find the syntax error that shows up in the output.

<?php
    ob_start();
    $phn=$_GET['phn'];
    $con = mysql_connect("<server>","<user>","<pass>") or die('error' . mysql_error());
    $db_selected = mysql_select_db('<db name>', $con);
    if (!$db_selected) {
        die ('Can\'t use user : ' . mysql_error());
    }
    $characters = 'abcdefghijklmnopqrstuvwxyz0123456789';
     $key= '';
     for ($i = 0; $i < 9; $i++) {
          $key.= $characters[rand(0, strlen($characters) - 1)];
     }
     echo $key;
    $sql="INSERT INTO buser (phone, key) VALUES (".$phn.",'".$key."')";
    if($result = mysql_query($sql ,$con) or die ('Error: '.mysql_error ()))
    {
    $q="SELECT * FROM buser WHERE phone=$phn";
    $idd=mysql_query($q,$con) or die ('Error: '.mysql_error ());
    while($row = mysql_fetch_assoc($idd))
      {
      $id=$row['bid'];
      }
    }
     ?>

Output:

Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'key) VALUES (9999,'ywfjj2dtc')' at line 1

Answer 1

KEY is a MySQL reserved keyword . You must enclose it in backticks to use it as a column or table identifier.

$sql="INSERT INTO buser (phone, `key`) VALUES (".$phn.",'".$key."')";

Your script is vulnerable to SQL injection in its current form. At a minimum, you must call mysql_real_escape_string() on the value of $phn .

$phn = mysql_real_escape_string($_GET['phn']);  

In the long term, consider switching to an API which supports prepared statements, like MySQLi or PDO.