在 PHP 和 Mysql 中实现 hashtable 的步骤

CREATE TABLE hashtable (
    id INT AUTO_INCREMENT PRIMARY KEY,
    key_name VARCHAR(255) NOT NULL,
    value_text TEXT NOT NULL
);

class Hashtable {
    private $db;

    public function __construct($db) {
        $this->db = $db;
    }

    public function set($key, $value) {
        $stmt = $this->db->prepare("INSERT INTO hashtable (key_name, value_text) VALUES (?, ?) ON DUPLICATE KEY UPDATE value_text = ?");
        $stmt->bind_param("sss", $key, $value, $value);
        $stmt->execute();
    }

    public function get($key) {
        $stmt = $this->db->prepare("SELECT value_text FROM hashtable WHERE key_name = ?");
        $stmt->bind_param("s", $key);
        $stmt->execute();
        $result = $stmt->get_result();
        if ($result->num_rows == 0) {
            return null;
        } else {
            $row = $result->fetch_assoc();
            return $row['value_text'];
        }
    }

    public function delete($key) {
        $stmt = $this->db->prepare("DELETE FROM hashtable WHERE key_name = ?");
        $stmt->bind_param("s", $key);
        $stmt->execute();
    }
}

$db = new mysqli("localhost", "username", "password", "database");
$hashtable = new Hashtable($db);

$hashtable->set("name", "John Doe");
$hashtable->set("age", "30");

echo $hashtable->get("name"); // 输出 "John Doe"
echo $hashtable->get("age"); // 输出 "30"

$hashtable->delete("age");
echo $hashtable->get("age"); // 输出 null