unable to connect to the database keep getting an unusual error

Question

I have created a class of DB and called that class on a page but I do not know what the problem is I keep getting an unusual error, found the similar issues on Google but couldn't have solved this problem.

This is the error :

SQLSTATE[HY000] [2002] php_network_getaddresses: getaddrinfo failed: Name or service not known

Here is my db class

class db {
    private $host;
    private $db_name;
    private $db_user;
    private $db_password;

    public function connect() {
        $db_name = $this->db_name;
        $db_user = $this->db_user;
        $db_pass = $this->db_password;
        $db_host = $this->host;

        $db_name = 'database name';
        $db_user = 'username';
        $db_pass = 'password';
        $db_host = 'localhost:3306';

        try {
            $connect = new PDO('mysql:dbname=$db_name;host=$db_host;', $db_user, $db_pass);
            $connect->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            echo "Connection Successfull";
        } catch(PDOException $e) {
            echo "Connection Failed : " . $e->getMessage();
        }
    }
}

This is the code I am using to test if this is only a warning or it is a failed connection to the data base

$users      = new users();
    $connection = new db();
    $connect    = $connection->connect();
    $sql = $connect->prepare("SELECT * FROM users");
    $sql->execute();
    while($data = $sql->fetch(PDO::FETCH_ASSOC)) {
        echo $data['name'];
    }

Answer 1

The single quotes (in ... new PDO('mysql:dbname=$db_name;host=$db_host;', ... ) don't interpolate/use the variables - with that code you are connecting to a machine called ' $host ', not the value of the $host variable.

My #1 debugging tip - print what is actually happening, not what you think must be - it's surprising how often something looks obviously right, but is clearly incorrect when properly shown what is actually being delivered to the system.

As for the $connect = $connection->connect(); line, yes - you need to return $connect; out of the function. That variable is what allows you to access the PDO functionality - it has the information within it about actually being able to talk to the database server. (In this instance, sending the SQL that you are first prepare -ing).