How to change variables in the .env file dynamically in Laravel?

Question

I want to create a Laravel web app that allows an admin user to change some variables(such as database credentials) in the .env file using the web backend system. But how do

Answer 1

To extend on lukasgeiter's and other's answer above, using regex to match the .env would be better, , as unlike app.key, the variable to put in .env may not be in the config.

Below is the code I used when experimenting on custom artisan command. This code generates a key for XChaCha encryption (XCHACHA_KEY=?????):

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$path = base_path('.env');
if (file_exists($path)) {
    //Try to read the current content of .env
    $current = file_get_contents($path);   

    //Store the key
    $original = [];
    if (preg_match('/^XCHACHA_KEY=(.+)$/m', $current, $original)) { 
    //Write the original key to console
        $this->info("Original XChaCha key: $original[0]"); 

    //Overwrite with new key
        $current = preg_replace('/^XCHACHA_KEY=.+$/m', "XCHACHA_KEY=$b64", $current);

    } else {
    //Append the key to the end of file
        $current .= PHP_EOL."XCHACHA_KEY=$b64";
    }
    file_put_contents($path, $current);
}
$this->info('Successfully generated new key for XChaCha');

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Using preg_match() allows the original key to be retrieved as needed, also allows the key to be changed even if the actual value is not known.