How to write logs from PHP to STDOUT/STDERR

[f3l1x]

Hi ✋ I've done some searching, but no luck.

Is it possible to write logs from PHP to console? I mean, I see logs from Caddy, FrankenPHP, but I do not know how to see logs from my app. Ofc, I can write it to file or some log service, but I would like to dump it to STDOUT/STDERR and collect by Grafana Promtail.

 ✔ Container demo-frankenphp-app-1  Created                                                                                                                                                                  0.0s
Attaching to app-1
app-1  | {"level":"info","ts":1729762707.532279,"msg":"using config from file","file":"/etc/caddy/Caddyfile"}
app-1  | {"level":"info","ts":1729762707.5329158,"msg":"adapted config to JSON","adapter":"caddyfile"}
app-1  | {"level":"warn","ts":1729762707.5329225,"msg":"Caddyfile input is not formatted; run 'caddy fmt --overwrite' to fix inconsistencies","adapter":"caddyfile","file":"/etc/caddy/Caddyfile","line":11}
app-1  | {"level":"info","ts":1729762707.5333776,"logger":"admin","msg":"admin endpoint started","address":"localhost:2019","enforce_origin":false,"origins":["//localhost:2019","//[::1]:2019","//127.0.0.1:2019"]}
app-1  | {"level":"warn","ts":1729762707.5334353,"logger":"http.auto_https","msg":"server is listening only on the HTTP port, so no automatic HTTPS will be applied to this server","server_name":"srv0","http_port":80}
app-1  | {"level":"info","ts":1729762707.5336876,"logger":"tls.cache.maintenance","msg":"started background certificate maintenance","cache":"0x40005e0880"}
app-1  | {"level":"info","ts":1729762707.5678976,"msg":"FrankenPHP started 🐘","php_version":"8.3.12","num_threads":21}
app-1  | {"level":"info","ts":1729762707.5680923,"logger":"http.log","msg":"server running","name":"srv0","protocols":["h1","h2","h3"]}
app-1  | {"level":"info","ts":1729762707.5683227,"msg":"autosaved config (load with --resume flag)","file":"/config/caddy/autosave.json"}
app-1  | {"level":"info","ts":1729762707.5683365,"msg":"serving initial configuration"}
app-1  | {"level":"info","ts":1729762707.5723917,"logger":"tls","msg":"storage cleaning happened too recently; skipping for now","storage":"FileStorage:/data/caddy","instance":"xx","try_again":1729849107.5723913,"try_again_in":86399.999999875}
app-1  | {"level":"info","ts":1729762707.572468,"logger":"tls","msg":"finished cleaning storage units"}

Thanks.

[withinboredom]

This is how we write logs and don't have any issues. Can you share what isn't working for you?

[f3l1x]

I mean, I wanted to write something like app-1 | {"level":"info", "message": "My custom text"} or something like that.

I've tried these functions.

fwrite(STDOUT, 'test');
fwrite(STDERR, 'test');
file_put_contents('php://stdout', 'Hello world');
file_put_contents('php://stderr', 'Hello world');

But not luck in here.

[dunglas]

Using error_log('Hello world', 4); should work. More details: https://www.php.net/manual/en/function.error-log.php