为什么这些UPDATE＆INSERT INTO查询不起作用？ PHP和MySQL

Question

I have 2 queries. Query #1 updates some things in the database, and Query #2 inserts some data into the table.

Code:

function add_like($id) {

    $connection = new mysqli($host, $username, $password, $database);

    $id = $connection->real_escape_string($id);

    $query = $connection->query("UPDATE `posts` SET `post_likes` = `post_likes` + 1 WHERE `id` = '$id'");
    $likes_query = $connection->query("INSERT INTO `likes` VALUES (".$_SESSION['user_login'].", $id)");
}

The first query ( $query ) should add 1 like to the database. So starting at 0 it should +1. Instead, it does +12.

The second query ( $likes_query ) does not INSERT INTO likes .

Any help would be much appreciated. Thanks!

---

UPDATE:

Changed the second query to:

$likes_query = $connection->query("INSERT INTO `likes` (`user_id`, `post_id`) VALUES ('$user', '$id')");

Answer 1

Final code:

function add_like($id) {
    if (isset($_SESSION['user_login'])) {
        $user = $_SESSION["user_login"];
    }
    else {
        $user = "";
    }

    $connection = new mysqli($host, $username, $password, $database);

    $id = $connection->real_escape_string($id);

    $query = $connection->query("UPDATE `posts` SET `post_likes` = `post_likes` + 1 WHERE `id` = '$id'");
    $likes_query = $connection->query("INSERT INTO `likes` (`user_id`, `post_id`) VALUES ('$user', '$id')");
}

All issues fixed. Thanks for all your comments!