Implementing a GraphQL server with components in PHP –

Implementing a GraphQL server with components in PHP

GraphQL is a query language for APIs, which gives clients the power to ask for exactly what data they need and receive exactly that, nothing more or less. This way, a single query can already fetch all the required data to render a component.

(A REST API, in comparison, must trigger several roundtrips to fetch data from multiple resources from different endpoints, which can become very slow, particularly on mobile.)

Even though GraphQL (which means “Graph Query Language”) uses a graph data model to represent data, the GraphQL server does not necessarily need to use a graph as the data structure to resolve the query, but can use any data structure that desires. The graph is only a mental model, not an actual implementation.

This is endorsed by the GraphQL project by stating on its website (emphasis mine):

Graphs are powerful tools for modeling many real-world phenomena because they resemble our natural mental models and verbal descriptions of the underlying process. With GraphQL, you model your business domain as a graph by defining a schema; within your schema, you define different types of nodes and how they connect/relate to one another. On the client, this creates a pattern similar to Object-Oriented Programming: types that reference other types. On the server, since GraphQL only defines the interface, you have the freedom to use it with any backend (new or legacy!).

This is good news, because dealing with either graphs or trees (which are subsets of graphs) is not trivial, and can lead to an exponential or logarithmic time complexity for resolving the query (i.e. the time required to resolve a query may increase several orders of magnitude for each new input to the query).

In this article, I will describe the architectural design of the GraphQL server in PHP GraphQL by PoP, which uses components as a data structure instead of graphs. This server owes its name to PoP, the library to build components in PHP over which it is based. (I am the author of both projects.)

This article is divided into 5 sections, explaining:

  1. What is a component
  2. How PoP works
  3. How components are defined in PoP
  4. How components are naturally suitable for GraphQL
  5. The performance of using components to resolve a GraphQL query

Let’s start.

1. What is a component

The layout of every webpage can be represented using components. A component is simply a set of pieces of code (such as HTML, JavaScript and CSS) put all together to create an autonomous entity, which can wrap other components to create more complex structures, and be itself wrapped by other components too. Every component has a purpose, which can range from something very basic, such as a link or a button, to something very elaborate, such as a carousel or a drag-and-drop image uploader.

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This article was written by Leo and originally published on WPKube.

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