Is your application observable? This is a question that starts to be relevant as the complexity of an application grows. To be able to monitor and observe what's going on at run-time is a crucial aspect for debugging issues and improving performance. In this talk we will present how to monitor a PHP application using OpenTelemetry. OpenTelemetry is an open source project incubated by Cloud Native Computing Foundation that allows developers to use a common standard to observe and collect metrics from any running applications. It provides a set of tools, APIs, and SDKs for many languages. In this talk we will present OpenTelemetry for PHP showing how to use the automatic and manual instrumentation tools for monitoring any application at runtime.