CREATE TABLE wp_tokens (
   ID int(12) NOT NULL AUTO_INCREMENT,
   USER varchar(128) NOT NULL COMMENT 'User name',
   TS timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
   IP varchar(64) NOT NULL,
   TOKEN varchar(128) NOT NULL COMMENT 'Hashed tokens',
   VALID (12),
   PRIMARY KEY (`ID`)
)

<?php
  global $wpdb;
  global $user_login;
  $token = uniqid();
  $hashedtoken = md5($token);
  $user = $user_login;
  $ip = $_SERVER['REMOTE_ADDR'];
  $valid = "1";
  $chkdb = mysql_query("SELECT valid FROM wp_tokens WHERE user=$user");

if(mysql_num_rows($chkdb) == 1)
{
    echo $hashedtoken;
}
else
    {
     $wpdb->insert('wp_tokens',
     array('user' => $user, 'token' => $hashedtoken, 'ip' => $ip, 'valid' => $valid),
     array('%s','%s','%s'));
    }
?>