Declaring private class variables based on conditional - php

Question

I have been trying to get better at OOP. I am writing a database class, which will handle simply connecting to a database via PDO. Now, I want to make it so that it uses different variables if it is being served from my localhost server.
Consider the following code:
<?php
class Database {
private $host;
private $name;
private $username;
private $password;
public $conn;
if ($_SERVER['SERVER_NAME'] == "localhost") {
$host = "change_to_your_db_host";
$name = "change_to_your_db_name";
$username = "change_to_your_db_username";
$password = "change_to_your_db_password";
}
else {
$host = "change_to_your_db_host";
$name = "change_to_your_db_name";
$username = "change_to_your_db_username";
$password = "change_to_your_db_password";
}
public function connect () {
$this->conn = null;
try {
$this->conn = new PDO("mysql:host=" . $this->host . ";dbname=" . $this->db_name, $this->username, $this->password);
}
catch (PDOException $exception) {
echo "Connection error: " . $exception->getMessage();
}
return $this->conn;
}
}
?>
I am very new to classes in general - I have been writing pure prodecural function-based PHP for wayyyy too long.
My questions are:
Is it cool to use $_SERVER variables within a class like that?
Is using that conditional statement within the class to determine the private variables OK? This class will be included in all of my other scripts which access the database via my object classes.
Is there a more efficient way to write this rather that have it echo an exception if one is caught?
I just want to make sure that I am doing things properly going forward. I have been writing PHP for a long time and I want to get out of the my outdated and archaic methods entirely.

Answer 1

You should do your conditional declaration in the __construct() method of your class like so:
<?php
class Database {
private $host;
private $name;
private $username;
private $password;
public $conn;
public function __construct()
{
if ($_SERVER['SERVER_NAME'] == "localhost")
{
$this->host = "change_to_your_db_host";
$this->name = "change_to_your_db_name";
$this->username = "change_to_your_db_username";
$this->password = "change_to_your_db_password";
}
else
{
$this->host = "change_to_your_db_host";
$this->name = "change_to_your_db_name";
$this->username = "change_to_your_db_username";
$this->password = "change_to_your_db_password";
}
}
public function connect () {
$this->conn = null;
try {
$conn = new PDO("mysql:host=" . $this->host . ";dbname=" . $this->db_name, $this->username, $this->password);
}
catch (PDOException $exception) {
throw $exception // you can throw again this \Exception to handle it in your code using the object
}
$this->conn = $conn;
return $this; // you should return $this so you can chain the object methods. Since $con is public, you can still access it
}
}
Is it cool to use $_SERVER variables within a class like that?
I cannot see why not.
Is using that conditional statement within the class to determine the private variables OK? This class will be included in all of my other scripts which access the database via my object classes.
As per #MarcB's comment, no you cannot run code at the top-level of a class, only in methods.
Is there a more efficient way to write this rather that have it echo an exception if one is caught?
Yes, throw it again so you can handle it in the final code using the Database class.