A Developer's Guide to Building PHP APIs

Creating Application Programming Interfaces (APIs) in PHP can be a powerful way to manage interactions between the backend of your application and various clients. Whether you’re building a PHP API for a web app, mobile app, or third-party integration, certain best practices and tools can make the process smoother and the results more reliable. 

This blog provides a guide to walk you through setting up a robust REST PHP API. I begin with initial setup considerations and outline which technologies will be needed to follow along, then move through various fundamentals, tools, and frameworks for building PHP APIs.

PHP API Setup: What to Know Before You Begin

Starting with PHP API development requires a good understanding of both backend fundamentals and PHP-specific frameworks and tools. Key considerations include:

• Purpose of the PHP API – Decide on the core functionality and goals of your PHP API. This will influence the structure, routes, and logic of the endpoints.
• Security Requirements– consider implementing authentication (like OAuth or JWT) and limiting request rates to protect your resources.
• Scalability – Choose tools and practices that allow the PHP API to scale, especially if you expect high traffic.

Having a clear understanding of these factors before you begin can help you select the right tools and frameworks for your project.

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Types of PHP APIs

Various types of PHP APIs are available for your project. Each has different strengths, so choose one that fits the use case of your application:

• REST (Representational State Transfer) APIs are best when you need simplicity and compatibility across many platforms.
• SOAP (Simple Object Access Protocol) APIs  are best for high-security, enterprise-grade applications.
• GraphQL APIs are best when clients need control over data and complex querying.
• JSON-RPC/XML-RPC are best for simple method-based calls and are typically used for internal applications.
• gRPC APIs are best for high-performance needs in microservices or real-time applications.

For the purposes of this guide, we decided to use REST APIs.

PHP API Requirements

To create a PHP API, ensure you have:

• PHP 8.0 or higher, with essential extensions like ext-json and ext-pdo
• Composer to manage dependencies
• A web server (Apache or nginx) with proper routing configuration
• Optional but beneficial libraries like roave/psr-container-doctrine, swagger-php, and development tools like PHP_CodeSniffer, PHPStan, and PHPUnit

How to Create APIs in PHP: Required Technologies for This Guide

The goal is to create API endpoints with PHP 8.3, while using best practices in all aspects possible. That said, we will focus on technologies like Mezzio as the backend framework, Swagger to showcase the endpoints, Doctrine as the ORM for database transactions, Docker to enable isolated local development, PSR-12 for the coding standard and Git as our version control system. In addition, we also utilize Psalm, PHPStan and PHPCodesniffer for static analysis.

Using Mezzio as Backend Framework

Mezzio is a micro-framework that’s ideal for building middleware applications like PHP APIs. Its middleware approach allows you to create flexible routing and streamlined request/response handling.

CLI Setup Example

To install Mezzio, use Composer:

composer create-project mezzio/mezzio-skeleton my-api

During setup, select FastRoute as the router. You can configure the initial structure based on your API needs, with specific endpoints and middlewares.