Azure Websites enables web applications deployment on a scalable and reliable cloud infrastructure. You can quickly scale up and down or even dynamically auto-scale to meet your application needs.
Azure provides different execution models for running applications. Each one provides a different set of services, so the one you choose depends on exactly what you're trying to do. Azure Websites is built on top of Azure Cloud Services to create a Platform as a Service solution optimized for running web applications based on PHP.
Symfony can be setup on Azure website as described in following tutorial: Deploying to Microsoft Azure Website Cloud