classes/Application.php
public function setEnvironment($environment)
	{
		if ($this->booting) {
			throw new \RuntimeException('Cannot set environment after application has booted');
		}

		if ($environment instanceof Closure) {
			$environment = call_user_func($environment);
		}

		if (!is_string($environment)) {
			throw new \InvalidArgumentException('Environment must be a string');
		}

		$this->environment = $environment;
	}
public function setEnvironment($environment)
	{
		if ($this->booting) {
			throw new \RuntimeException('Cannot set environment after application has booted');
		}

		if ($environment instanceof Closure) {
			$environment = call_user_func($environment);
		}

		if (!is_string($environment)) {
			throw new \InvalidArgumentException('Environment must be a string');
		}

		$this->environment = $environment;
	}
Set the environment of the application. Has to be called before boot().

@param string $environment