protected function decode($string)
{
    $string=preg_replace(
        array('/"\s+"/','/\\\\n/','/\\\\r/','/\\\\t/','/\\\\"/'),
        array('',"\n","\r","\t",'"'),
        $string
    );
    return substr(rtrim($string),1,-1);
}

protected function encode($string)
{
    return str_replace(
        array('"',"\n","\t","\r"),
        array('\\"',"\\n",'\\t','\\r'),
        $string
    );
}

public function load($file,$context)
{
    $pattern='/(msgctxt\s+"(.*?(?<!\\\\))")?\s+'
        .'msgid\s+((?:".*(?<!\\\\)"\s*)+)\s+'
        .'msgstr\s+((?:".*(?<!\\\\)"\s*)+)/';
    $matches=array();
    $n=preg_match_all($pattern,file_get_contents($file),$matches);

    $messages=array();
    for($i=0; $i<$n; $i++)
    {
        if($matches[2][$i]===$context)
        {
            $id=$this->decode($matches[3][$i]);
            $message=$this->decode($matches[4][$i]);
            $messages[$id]=$message;
        }
    }
    return $messages;
}

public function save($file,$messages)
{
    $content='';
    foreach($messages as $id=>$message)
    {
        if(($pos=strpos($id,chr(4)))!==false)
        {
            $content.='msgctxt "'.substr($id,0,$pos)."\"\n";
            $id=substr($id,$pos+1);
        }
        $content.='msgid "'.$this->encode($id)."\"\n";
        $content.='msgstr "'.$this->encode($message)."\"\n\n";
    }
    file_put_contents($file,$content);
}