escapJSON

  function escapeJsonString($value) {
    # list from www.json.org: (\b backspace, \f formfeed)    
    $escapers =     array("\\",     "/",   "\"",  "\n",  "\r",  "\t", "\x08", "\x0c");
    $replacements = array("\\\\", "\\/", "\\\"", "\\n", "\\r", "\\t",  "\\f",  "\\b");
    $result = str_replace($escapers, $replacements, $value);
    return $result;
  }
  
  $mongo = array('d','48na03af');
  echo escapeJsonString(json_encode($ary));