Store session in database

CREATE TABLE sessions (
  id CHAR(32) NOT NULL,
  data TEXT,
  last_accessed TIMESTAMP NOT NULL,
  PRIMARY KEY (id)
);

<?php /**
 * Created by PhpStorm.
 * User: michaeldu
 * Date: 15/7/14
 * Time: 下午2:57
 */
$sdbc = NULL;

function open_session() {
    global $sdbc;
    $sdbc = mysqli_connect('192.168.31.172', 'root', 'root', 'phpadvanced');
    return true;
}

function close_session() {
    global $sdbc;
    return mysqli_close($sdbc);
}

function read_session($sid) {
    global $sdbc;
    $q = sprintf('SELECT data FROM sessions WHERE ', mysqli_real_escape_string($sdbc, $sid));
    $r = mysqli_query($sdbc, $q);

    if (mysqli_num_rows($r) == 1) {
        list($data) = mysqli_fetch_array($r, MYSQLI_NUM);
        return $data;
    } else {
        return '';
    }
}

function write_session($sid, $data) {
    global $sdbc;

    $q = sprintf('REPLACE INTO sessions (id, data) VALUES ("%s", "%s")', mysqli_real_escape_string($sdbc, $sid), mysqli_real_escape_string($sdbc, $data));
    $r = mysqli_query($sdbc, $q);
    return true;
}

function destroy_session($sid) {
    global $sdbc;
    $q = sprintf('DELETE FROM session WHERE', mysqli_real_escape_string($sdbc, $sid));
    $r = mysqli_query($sdbc, $q);

    $_SESSION = array();

    return true;
}

function clean_session($expire) {
    global $sdbc;

    $q = sprintf('DELETE FROM sessions WHERE DATE_ADD(last_accessed, INTERVAL %d SECOND) < NOW()', (int)$expire);
    $r = mysqli_query($sdbc, $q);

    return true;
}

session_set_save_handler('open_session', 'close_session', 'read_session', 'write_session', 'destroy_session', 'clean_session');

session_start();

<?php /**
 * Created by PhpStorm.
 * User: michaeldu
 * Date: 15/7/14
 * Time: 下午3:14
 */
require('db_session.inc.php');
?>




    <title>colour_blue</title>
    <meta name="description" c>
    <meta name="keywords" c>
    <meta http-equiv="content-type" c>
    <link rel="stylesheet" type="text/css" href="/phpadvanced/02developwebapplication/style/style.css" title="style">



<?php if(empty($_SESSION)) {
    $_SESSION['blah'] = 'umlaut';
    $_SESSION['this'] = 3615684.45;
    $_SESSION['that'] = 'blue';
    echo '<p>Session已存储';
} else {
    echo '<p>SESSION已存在, </p><pre class="brush:php;toolbar:false">'.print_r($_SESSION, 1).'

'; } if(isset($_GET['logout'])) { session_destroy(); echo '

会话结束

'; } else { echo '登出'; } echo '

会话数据:

'.print_r($_SESSION, 1).'

'; ?>

The above introduces the storage of sessions in the database, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.