class ini {
    protected $lines;

    public function read($file) {
        $this->lines = array();

        $section = '';

        foreach(file($file) as $line) {
            // comment or whitespace
            if(preg_match('/^\s*(;.*)?$/',$line)) {
                $this->lines[] = array('type' => 'comment','data' => $line);
            // section
            } elseif(preg_match('/\[(.*)\]/',$line,$match)) {
                $section = $match[1];
                $this->lines[] = array('type' => 'section','data' => $line,'section' => $section);
            // entry
            } elseif(preg_match('/^\s*(.*?)\s*=\s*(.*?)\s*$/',$match)) {
                $this->lines[] = array('type' => 'entry','section' => $section,'key' => $match[1],'value' => $match[2]);
            }
        }
    }

    public function get($section,$key) {
        foreach($this->lines as $line) {
            if($line['type'] != 'entry') continue;
            if($line['section'] != $section) continue;
            if($line['key'] != $key) continue;
            return $line['value'];
        }

        throw new Exception('Missing Section or Key');
    }

    public function set($section,$key,$value) {
        foreach($this->lines as &$line) {
            if($line['type'] != 'entry') continue;
            if($line['section'] != $section) continue;
            if($line['key'] != $key) continue;
            $line['value'] = $value;
            $line['data'] = $key . " = " . $value . "\r\n";
            return;
        }

        throw new Exception('Missing Section or Key');
    }

    public function write($file) {
        $fp = fopen($file,'w');

        foreach($this->lines as $line) {
            fwrite($fp,$line['data']);
        }

        fclose($fp);
    }
}

$ini = new ini();
$ini->read("C:\\PHP.ini");
$ini->set('PHP','engine','Off');
echo $ini->get('PHP','engine');
$ini->write("C:\\PHP.ini");