Calling single db connection using static method - php

Question

I tried to follow the structure factory in creating a single db connection as per below:
try {
$provider = function() {
$instance = new PDO("dsn", "username", "password");
return $instance;
};
} catch (PDOException $exception) {
error_log($exception->getMessage());
}
$factory = new StructureFactory($provider);
and StructureFactory as below:
class StructureFactory {
protected $provider = null;
protected $connection = null;
public function __construct(callable $provider) {
$this->provider = $provider;
}
public function create($class_name) {
if ($this->connection === null) {
$this->connection = call_user_func($this->provider);
}
return new $class_name($this->connection);
}
}
Then when I need to create a book instance, say "Book", I do this:
$factory->create("Book");
But if I don't need to create a book instance yet but just want to check if that book is existing, I'd like to call a static method on my "Book" class like:
Book::isBookExisting($bookname);
But inside this static method, how can I have the single database connection if I can only have it when I create the "Book" instance?
Or should I just use a Singleton for my db connection instead of doing this factory?
I am kinda at lost cause I'm not sure if I am doing it correctly. Please advise.

Answer 1

First
The way you've written the try catch block is mostly useless and certainly not doing as you expect.
try {
$provider = function() {
$instance = new PDO("dsn", "username", "password");
return $instance;
};
} catch (PDOException $exception) {
error_log($exception->getMessage());
}
Remember, $provider = function() { ... is an anonymous function. The code inside it only runs when the function is called. In other words, the code inside the try block, in your example, will never throw an exception. It will only ever throw an exception when is is called e.g. $provider().
Refactored
$provider = function() {
try {
$instance = new PDO("dsn", "username", "password");
} catch (PDOException $exception) {
error_log($exception->getMessage());
}
return $instance;
};
The database connection
There are too many ways to solve the database dependency issue, many of which are opinionated. There is no one solution.
You could:
Use a singleton
Use a argument dep. Book::isBookExisting($provider, $bookname);
Use a static dep. Book::setProvider($provider); Book::isBookExisting($bookname);
...
Further Reading:
Dependency Injection