Post a message to a slack channel with PHP

PostMessageToSlackChannel.php

<?php

/**
 * Send a Message to a Slack Channel.
 *
 * In order to get the API Token visit: 
 *
 * 1.) Create an APP -> https://api.slack.com/apps/
 * 2.) See menu entry "Install App"
 * 3.) Use the "Bot User OAuth Token"
 *
 * The token will look something like this `xoxb-2100000415-0000000000-0000000000-ab1ab1`.
 * 
 * @param string $message The message to post into a channel.
 * @param string $channel The name of the channel prefixed with #, example #foobar
 * @return boolean
 */
function slack($message, $channel)
{
    $ch = curl_init("https://slack.com/api/chat.postMessage");
    $data = http_build_query([
        "token" => "YOUR_API_TOKEN",
    	"channel" => $channel, //"#mychannel",
    	"text" => $message, //"Hello, Foo-Bar channel message.",
    	"username" => "MySlackBot",
    ]);
    curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
    curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
    $result = curl_exec($ch);
    curl_close($ch);
    
    return $result;
}

// Example message will post "Hello world" into the random channel
slack('Hello world', '#random');

I did get invalid_payload response. Issue was with $data, I had to pass it as json:

    function slack($message, $channel)
    {
        $url = getenv('SLACK_WEBHOOK_URL');
        $ch = curl_init($url);
        $data = [
            'channel' => $channel,
            'text' => $message,
            'username' => 'SlackBot',
        ];
        curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'POST');
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data, JSON_THROW_ON_ERROR, 512));
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);

        $result = curl_exec($ch);
        curl_close($ch);

        return $result;
    }

Legacy tokens creation disabled...

Yeah from:

https://api.slack.com/legacy/custom-integrations/legacy-tokens

Legacy token management
Tokens may no longer be created, but you can re-issue existing tokens here.

I needed a simple test so now have to look for another PHP example...

The code still works but you have to use Bot User OAuth Token which requires to:

1.) Create an APP -> https://api.slack.com/apps/
2.) See menu entry "Install App"
3.) Use the "Bot User OAuth Token"

The file_get_contents() version:

function slack($message, $channel)
{
  $url = "https://slack.com/api/chat.postMessage";

  $data = http_build_query([
    "token" => getenv('SLACK_BOT_TOKEN'), // the "Bot User OAuth Token" value
    "channel" => $channel,
    "text" => $message,
    "username" => "NotificationBot",
  ]);

  $context = stream_context_create([
    'http' => [
      'method'  => 'POST',
      'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
      'content' => $data,
      'ignore_errors' => true // This is useful to get the content of the response even if the status code is not 200
    ]
  ]);

  $result = file_get_contents($url, false, $context);

  return $result;
}