How Can I Access Global Variables Within a PHP Class?

Accessing Global Variables from Within a Class

In your code, you're experiencing an error when trying to access a variable defined outside the class within a class method. This issue arises because accessing global variables directly from within a class is generally not recommended in PHP. However, there are a few methods to achieve this:

Dependency Injection

The preferred approach is to implement dependency injection. This involves passing the database object as an argument to the class constructor, allowing the class to access and utilize the variable without the need for global scope.

class Paginator
{
    private $db;

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

    // ...
}

// Usage:
$db = new DB_MySQL("localhost", "root", "", "test");
$pagination = new Paginator($db);

Injecting Instance into Methods

Alternatively, you can inject the database instance directly into the method that requires it.

class Paginator
{
    public function get_records($q, DB_MySQL $db)
    {
        // ...
    }
}

// Usage:
$pagination = new Paginator();
$pagination->get_records("SELECT * FROM `table`", $db);

Using Global Scope

While it's generally discouraged, you can use the global keyword to access global variables within a class method. However, this technique may clutter the code and make it less maintainable.

class Paginator
{
    public function get_records($q)
    {
        global $db;

        // ...
    }
}

// Usage:
$db = new DB_MySQL("localhost", "root", "", "test");
$pagination = new Paginator();

Remember that using global variables from within a class comes with potential downsides, including dependency issues, reduced testability, and code clarity issues. Therefore, it's recommended to consider dependency injection or injecting instances into methods when accessing variables from outside a class in PHP.

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