How to set .env values in laravel programmatically on the fly

Question

I have a custom CMS that I am writing from scratch in Laravel and want to set env values i.e. database details, mailer details, general configuration, etc from

Answer 1

tl;dr

Based on vesperknight's answer I created a solution that doesn't use strtok or env().

private function setEnvironmentValue($envKey, $envValue)
{
    $envFile = app()->environmentFilePath();
    $str = file_get_contents($envFile);

    $str .= "\n"; // In case the searched variable is in the last line without \n
    $keyPosition = strpos($str, "{$envKey}=");
    $endOfLinePosition = strpos($str, PHP_EOL, $keyPosition);
    $oldLine = substr($str, $keyPosition, $endOfLinePosition - $keyPosition);
    $str = str_replace($oldLine, "{$envKey}={$envValue}", $str);
    $str = substr($str, 0, -1);

    $fp = fopen($envFile, 'w');
    fwrite($fp, $str);
    fclose($fp);
}

Explanation

This doesn't use strtok that might not work for some people, or env() that won't work with double-quoted .env variables which are evaluated and also interpolates embedded variables

KEY="Something with spaces or variables ${KEY2}"