Example Login

    /* Snippet #1 */
    <?php
    // login_check.php
    define("server", "your_server");
    define("user", "your_name");
    define("password", "your_pass");
    define("name", "your_dbname");

    var $connection;
    $this->connection = mysql_connect(server,user,pass) or die(mysql_error());
    mysql_select_db(name, $this->connection) or die(mysql_error());

    function is_logged_in () {
      if (!($_SESSION["id"]) || ($_SESSION["id"] == "") || ($_SESSION["id"] == 0)) {
        Header("Location: ./login.php");
        exit();
      }
    }

    function clean_input($input) {

      $clean = array("\\",'<','>','`',':',';','/','(',')','{','}','[',']');
      //$with = array();
      return str_ireplace($clean,'', $input);
    }

    function login_check ($forms) {
      $error = "";
      $username = clean_input($forms["username"]);
      $password = clean_input($forms["password"]);
      if (trim($username) == "") $error .= "<li>Your username is empty.</li>";
      if (trim($password) == "") $error .= "<li>Your password is empty.</li>";
      /* from here, do your sql query to query the database to search for existing record with correct username and password */
      $query = "SELECT password, username FROM users WHERE username = '".mysql_real_escape_string($username)."' AND password = '".mysql_real_escape_string($password)."'";
      $result = mysql_query($query, $this->connection);
      if(!$result || (mysql_numrows($result) < 1)) {
         $error = "Invalid username or password";
      }else
          {
            $error = "";
          }
      if (trim($error)!="") return $error;
    }

    function login ($forms) {
      $username = clean_input($forms["username"]);
      $password = clean_input($forms["password"]);
      /* do your sql query again, but now returning the id of member */
      $query = "SELECT member_id FROM users WHERE username = '".mysql_real_escape_string($username)."' AND password = '".mysql_real_escape_string($password)."'";
      $result = mysql_query($query, $this->connection);
      $result = mysql_query($query, $this->connection);
      if(!$result || (mysql_numrows($result) < 1)) {
         $id = 0;
      }else
          {
            $id = $result;
          }
      return $id;
    }
    ?>






    /* Snippet #2 */
    <?php
    // login.php
    session_start();
    include ("login_check.php");
    if ($_POST) {
      $error = login_check($_POST);
      if (trim($error)=="") {
        $_SESSION["id"] = login($_POST);
        Header("Location: ./index.php") /* Redirect validated member */
        exit();
      } else {
        print "Error:$error";
      }
    }
    ?>

    /* Snippet #3 */
    <?php
      // index.php
      include("login_check.php");
      session_start();
      is_logged_in();
    ?>