Set a php object global for query optimization - php

Question

I have a problem in optimizing my PHP script. For example:
A MySQL Table:
option_name || option_value
=====================================================
base_url || http://mysite.com/myproject
theme_name || default
language || en
MyScript.php file:
class options {
private $options = null;
public function get($optionName) {
if(!isset($this->options))
self::get_data();
return $this->options[$optionName];
}
protected function get_Data() {
// ...
// DO A MYSQL QUERY AND SAVE IT TO $this->options
// ...
}
}
The data which this class returns is constant. So there is no need to run a MySQL query every time I need to access for example base_url value. What is the best way to create an object and use it global?
$OPTIONS = new options;
function load_option($optName) {
global $OPTIONS;
return $OPTIONS->get($optName);
}
Something like this function maybe? Someone told this is The Worst Possible Way.
I need help. Thanks!

Answer 1

Your problem here, is that you do not understand what SOLID and DI principles are. You should implement classes that serve each singular responsibility, then inject their instances on demand.
In your case, it would look like this,
class Config
{
protected $pdo;
protected $cache;
public function __construct($pdo)
{
$this->pdo = $pdo;
}
public function read($key)
{
// Read a value by its key from a table
// Here should be a SELECT query
// You can also prevent reading the same thing twice
// by storing it in a cache
}
public function write(array $data)
{
foreach ($data as $key => $value) {
// Here should be INSERT statement
}
}
public function delete($key)
{
// Here comes a DELETE statement
}
}
Each time you need to read a configuration value, you would simply inject an instance of Config to a class that needs it.
class Foo
{
protected $config;
public function __construct(Config $config)
{
$this->config = $config;
}
public function doSomethingDependingOnConfig()
{
if ($this->config->read('lang') === 'en') {
// do something
}
}
}
And you would use it like,
$pdo = new PDO(...);
$config = new Config($pdo);
// Test
echo $config->read('lang'); //en
// So,
$foo = new Foo($config);
$foo->doSomethingDependingOnConfig();

Answer 2

Actually, I don't think that's the worst possible way.
Many config settings don't need to be stored in a database. Some even can't be (like the address and credentials of the database).
So is it obvious that some hard coded config is convenient. And if you would investigate existing PHP applications, you'll see that most of them will have some globally configurable options.
The disadvantage of a global variable, is that its very strict and hard to change it's usage. Soon you'll find yourself using this global thoughout your application.
But you already countered that by wrapping access to it in a function, so you can easily change the options later, without having to change your entire application. You've hidden the way the options are stored by making this wrapper function. If you'd like, you could still fetch them from the database, or start storing them in a file, because all you need to change is this function. So this is quite a good solution, actually.
One thing you could do to improve this code:
Maybe you could wrap it in a Config singleton class. The advantage of that, is that you can actually store the config in that class as well, getting rid of the global variable, and therefor, getting rid of accidental access to that global. You will force yourself to always use the function/class access to the options.