Check RSS feed and post to slack, if there is a new article

rss_slackpost.php

<?php

// Usage: /usr/bin/php rss_slackpost.php
// Require: php-xmlrpc, php-cli
// Make slack app. and get slackapikey, then invite bot
// $ cat feedlog.txt --> The URL of the newest article in the last check
//    https://example.org/wp/archives/178

ini_set("auto_detect_line_endings", true);

$slackchannel = 'channel_name';
$mess = '';
$fg = 0;
$feedurl = 'https://example.org/wp/feed';
$slackApiKey = 'xoxb-1234567890000-1234567890000-xxxxxxxxxxxxxxxxxxxxxxxx';
$log = './feedlog.txt';

$feed = file_get_contents($feedurl);

$invalid_characters = '/[^\x9\xa\x20-\xD7FF\xE000-\xFFFD]/';
$feed = preg_replace($invalid_characters, '', $feed);

$rss = simplexml_load_string($feed);

//var_dump($rss);

$fp = fopen($log, 'r+');
$oldurl = rtrim(fgets($fp, 4096));
fclose($fp);

foreach($rss->channel->item as $item){
   $link = $item->link;
   if (rtrim($link) == $oldurl) {
      break;
   }
   else {
      $mess = 'Newly posted'.PHP_EOL;
      $mess .= '----------------------------------------'.PHP_EOL;
      $title = $item->title;
      $date = $item->pubDate;
      //$description = strip_tags($item->description);
      $mess .= $title.PHP_EOL; 
      $mess .= $date.PHP_EOL; 
      $mess .= $link.PHP_EOL;
      if ($fg == 0) {
        file_put_contents($log, $link);
        $fg = 1;
      }
      $mess = urlencode($mess);
      $url = "https://slack.com/api/chat.postMessage?token=${slackApiKey}&channel=%23${slackchannel}&text=${mess}&as_user=true";
      $res = file_get_contents($url);
      echo $res;
      //break;
   }
}
?>