如何在配置文件中更改行

I have a file called settings.php that has all of the settings that the software uses. The problem is that I need users to be able to change the config without editing the file. I know I could do this with preg_replace but with dynamic settings like 'Board name' it would get tricky. I've tried a few things that didn't seem to work. I now you're not going to write the code for me, I just need a starting point.

Settings File

$settings = array (
    'home_display'=>'home',
    'db_host'=>'localhost',
    'db_user'=>'root',
    'db_password'=>'',
    'db'=>'',
    'login_enabled'=>true,
    'signup_enabled'=>true,
    'site_name'=>'Cheesecake Portal',
    'b_url'=>'beta.cheesecakebb.org',
    'b_email'=>'symbiote@cheesecakeb.org',
    'board_enabled'=>true
    );

The idea i have is to rewrite the file on the fly, even if i think this isnt the best way, it's a way.

if( file_exists($mySettingsFile) ){
    include($mySettingsFile);
}
else{
    $settings = array (         // the default settings array
        'home_display'=>'home',
        'db_host'=>'localhost',
        'db_user'=>'root',
        'db_password'=>'',
        'db'=>'',
        'login_enabled'=>true,
        'signup_enabled'=>true,
        'site_name'=>'Cheesecake Portal',
        'b_url'=>'beta.cheesecakebb.org',
        'b_email'=>'symbiote@cheesecakeb.org',
        'board_enabled'=>true
    );
}

// modifiy your settings here searching the key(s) you want to modify

// then put it in the config file
file_put_contents($mySettingsFile, '<?php '.var_export($settings).' ?>');

I hope this will illustrate my idea good enough to help you.