Add a Slackbot handler

This is the simplest way to log to Slack using the Slackbot.
It supports only plain text with automatic linking of URLs and mentions.

src/Monolog/Handler/SlackbotHandler.php

@@ -0,0 +1,84 @@
+<?php
+
+/*
+ * This file is part of the Monolog package.
+ *
+ * (c) Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Monolog\Handler;
+
+use Monolog\Logger;
+
+/**
+ * Sends notifications through Slack's Slackbot
+ *
+ * @author Haralan Dobrev <hkdobrev@gmail.com>
+ * @see    https://slack.com/apps/A0F81R8ET-slackbot
+ */
+class SlackbotHandler extends AbstractProcessingHandler
+{
+    /**
+     * The slug of the Slack team
+     * @var string
+     */
+    private $slackTeam;
+
+    /**
+     * Slackbot token
+     * @var string
+     */
+    private $token;
+
+    /**
+     * Slack channel name
+     * @var string
+     */
+    private $channel;
+
+    /**
+     * @param  string $token   Slackbot token
+     * @param  string $channel Slack channel (encoded ID or name)
+     * @param  int    $level   The minimum logging level at which this handler will be triggered
+     * @param  bool   $bubble  Whether the messages that are handled can bubble up the stack or not
+     */
+    public function __construct(
+        $slackTeam,
+        $token,
+        $channel,
+        $level = Logger::CRITICAL,
+        $bubble = true
+    ) {
+        parent::__construct($level, $bubble);
+
+        $this->slackTeam = $slackTeam;
+        $this->token = $token;
+        $this->channel = $channel;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @param array $record
+     */
+    protected function write(array $record)
+    {
+        $slackbotUrl = sprintf(
+            'https://%s.slack.com/services/hooks/slackbot?token=%s&channel=%s',
+            $this->slackTeam,
+            $this->token,
+            $this->channel
+        );
+
+        $ch = curl_init();
+        curl_setopt($ch, CURLOPT_URL, $slackbotUrl);
+        curl_setopt($ch, CURLOPT_POST, true);
+        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
+        curl_setopt($ch, CURLOPT_POSTFIELDS, $record['message']);
+
+        Curl\Util::execute($ch);
+    }
+}