I have a plugin and I am creating a css file in wp_content.

I used this:

    $this->content_dir = WP_CONTENT_DIR . "/some_folder";
 
    $path = $this->content_dir . 'options.css';
    $css='some string';
    global $wp_filesystem; 
    if(!$wp_filesystem->put_contents( $path, $css, 0644) ) {
	    return __('Failed to create css file');
    }

However I get this error:

Fatal error: Call to a member function put_contents() on a non-object 

var_dump($css) return string.

Does put_contents write to an exisiting file or does it create a file like file_put_contents does?

I am looking for an equivalent of this:

    if(!file_put_contents($path, $css)){
		return __('Failed to create css file');
	};

Thank you!