I keep running into an Nginx 502 Bad Gateway error when trying to send images through my Telegram bot. The weird thing is that basic API calls like getMe work perfectly fine.
I’m using Guzzle version 5.3.0 for PHP compatibility reasons. Is this the right approach for uploading photos or am I missing something? Any help would be appreciated!
This isn’t a server resource issue - it’s your Guzzle config. You’re using an outdated approach with the body parameter for file uploads. Since you’re on Guzzle 5.3.0, you need to use ‘multipart’ properly. Try this instead: $httpClient->post($url, ['multipart' => [['name' => 'chat_id', 'contents' => '123456789'], ['name' => 'photo', 'contents' => fopen($_FILES['imageUpload']['tmp_name'], 'r'), 'filename' => $_FILES['imageUpload']['name']]]]). This won’t load the entire file into memory like your current fread approach. The 502 error is happening because your web server can’t handle the malformed request you’re sending to Telegram’s API.
That 502 error screams resource limits. I had the same issue - turns out I was loading entire files into memory with fread() before sending them. Big images will kill your server’s memory allocation fast. Switch to CURLFile or use fopen() with streaming instead of reading the whole file at once. Also check your php.ini - bump up memory_limit and max_execution_time. Since getMe works fine, your bot token’s good and connectivity’s solid. It’s just image uploads choking your server. Try resizing images first or use chunked uploads if you’re dealing with consistently large files.
nginx 502 usually means php-fpm crashed from memory issues. Add timeout settings to your guzzle request: [‘timeout’ => 30, ‘connect_timeout’ => 10]. Check if your images are too big - telegram has size limits. Test with a tiny image first to see if it still breaks.
Been there. The real issue isn’t just memory or multipart handling - you’re doing this the hard way.
I spent weeks fighting similar 502 errors with image uploads until I realized I was overcomplicating everything. Sure, you can fix the Guzzle multipart thing and tune your server settings. But why deal with all that complexity when you can automate the whole pipeline?
Set up an automation workflow that handles file validation, resizing, and Telegram API calls with proper error handling and retries built in. No more memory crashes from loading huge files. No more 502 headaches from malformed requests.
I switched our entire bot infrastructure to this approach and haven’t touched a single line of upload code since. The workflow automatically processes images, handles all the API formatting, and even queues failed uploads for retry.
Your current PHP approach works for simple cases but breaks under load. Automation workflows scale without the server resource drama.
Your file upload method is the problem. You’re sending raw binary data, but Telegram’s API needs multipart/form-data encoding. Switch your Guzzle request to use the multipart option instead of dumping file content in the body parameter. Also check your server’s client_max_body_size and upload_max_filesize settings - 502 errors usually mean the upstream server is timing out or rejecting oversized requests. I had the same issue with my bot until I fixed the multipart handling. Night and day difference.
The 502 error happens because you’re not handling the file stream correctly with Telegram’s API. I hit this same issue when migrating an old bot from shared hosting. It’s not just multipart formatting - it’s how you manage the file resource. When you use fread() to load the whole file into a variable, you create a memory spike that triggers upstream timeouts, especially with strict FastCGI limits. Don’t read file data into memory. Pass the file handle directly through Guzzle’s multipart stream handling instead. This keeps memory usage low and stops the server from choking on larger images. Also check your FastCGI timeout settings - most hosting providers set these pretty low by default, causing 502 errors even on valid requests that take more than a few seconds.