Codeigniter environment setter - CI Library

environment_setter.php

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class Environment_setter
{
	protected $environment_file;
	protected $previous_environment;

	public function __construct()
	{
		$this->environment_file = dirname(__FILE__)."/../../index.php";
	}

	public function set_development_environment()
	{
		$this->previous_environment = $this->get_current_environment();
		$file_contents = file_get_contents($this->environment_file);

	    $new_content = str_replace("define('ENVIRONMENT', '$this->previous_environment');", "define('ENVIRONMENT', 'development');", $file_contents);

	    file_put_contents($this->environment_file, $new_content);
	}

	public function set_production_environment()
	{
		$this->previous_environment = $this->get_current_environment();
		$file_contents = file_get_contents($this->environment_file);

	    $new_content = str_replace("define('ENVIRONMENT', '$this->previous_environment');", "define('ENVIRONMENT', 'production');", $file_contents);

	    file_put_contents($this->environment_file, $new_content);
	}

	public function set_testing_environment()
	{
		$this->previous_environment = $this->get_current_environment();
		$file_contents = file_get_contents($this->environment_file);

	    $new_content = str_replace("define('ENVIRONMENT', '$this->previous_environment');", "define('ENVIRONMENT', 'testing');", $file_contents);

	    file_put_contents($this->environment_file, $new_content);
	}

	public function set_previous_environment()
	{
		$file_contents = file_get_contents($this->environment_file);
	    $new_content = str_replace("define('ENVIRONMENT', 'development');", "define('ENVIRONMENT', '$this->previous_environment');", $file_contents);
	    file_put_contents($this->environment_file, $new_content);

		$file_contents = file_get_contents($this->environment_file);
	    $new_content = str_replace("define('ENVIRONMENT', 'production');", "define('ENVIRONMENT', '$this->previous_environment');", $file_contents);
	    file_put_contents($this->environment_file, $new_content);

		$file_contents = file_get_contents($this->environment_file);
	    $new_content = str_replace("define('ENVIRONMENT', 'testing');", "define('ENVIRONMENT', '$this->previous_environment');", $file_contents);
	    file_put_contents($this->environment_file, $new_content);
	}

	protected function get_current_environment()
	{
		if(strpos(file_get_contents($this->environment_file), "define('ENVIRONMENT', 'production');"))
			return 'production';

		if(strpos(file_get_contents($this->environment_file), "define('ENVIRONMENT', 'development');"))
			return 'development';

		if(strpos(file_get_contents($this->environment_file), "define('ENVIRONMENT', 'testing');"))
			return 'testing';
	}

}