PHP Monolith to Microservices: When to Split Web Applications

PHP microservices and monolithic architectures are two fundamental approaches to building web applications, with each shaping how apps are developed, deployed, and scaled. Choosing the right architecture, or knowing when it's time to migrate from a PHP monolith to microservices, is crucial for your project's long-term performance, scalability, and security. However, making the move to microservices is more than the "lift-and-shift" many anticipate, and teams must be prepared for the complexities involved.

In this blog, I compare PHP microservices and monolithic architecture, exploring their features, advantages, and drawbacks. Next, I go through how microservices can benefit your application in the modern ecosystem, and outline a few key considerations for teams considering migrating from a PHP monolith to microservices.

PHP Architecture Overview: Monolithic vs. Microservices

As PHP applications grow, choosing the right architecture becomes critical. Two dominant paradigms — monolithic and microservices — offer distinct advantages and trade-offs depending on your project’s size, complexity, and team structure. 

The table below provides a quick-reference comparison to help you understand the key differences between PHP monoliths and microservices, followed by a more in-depth exploration of each PHP architecture type.

PHP Monolithic Architecture

A monolithic architecture refers to a software design where all components of an application are integrated as a single codebase and deployed as one unit. This structure is common in traditional PHP applications, where everything runs together on the same server.

Monolithic PHP applications are straightforward to build and manage, especially for small teams or projects with limited scope. They benefit from centralized control, simplified debugging, and faster initial development cycles.

However, a drawback is that when applications grow in size and complexity, monoliths can become harder to maintain. Tight coupling between modules can slow down development, complicate testing, and make scaling specific features more difficult. These limitations often prompt teams to consider transitioning to a microservices architecture.

PHP Microservices Architecture

PHP microservices architecture is a design approach where an application is separated into a collection of loosely coupled, independently deployable services. Each service is responsible for a specific business capability, such as user authentication or content delivery, and communicates with other services via lightweight protocols.

This modular structure allows teams to build, scale, and maintain services separately. Unlike monolithic applications, where all functionality resides in a single codebase, microservices promote separation of concerns and service autonomy. This leads to faster development cycles and improved fault isolation.

Microservices are particularly well-suited for large, complex applications with multiple teams working in parallel. However, they can also introduce challenges such as increased operational overhead, distributed data management, and the need for comprehensive monitoring and security practices.

When to Split a PHP Monolith to Microservices

While the best time to plan an application’s architecture is at the beginning, it is hard to predict the future of an application at its inception. Software architects struggle to plan for the unknown, leading to over-engineering at increased maintenance cost, or falsely anticipating what features customers will use most. Therefore, regular analysis of an application is important and should be planned periodically.

By performing a detailed analysis of an application, including code, infrastructure, traffic, load, deployment processes, and consumed resources, the need to take action surfaces early. Following, we will discuss some of the most common vectors to be found.

Minimize Bottlenecks in Development and Deployment

Deployment bottlenecks may be alleviated by extracting portions of a PHP application to microservices. Doing so can increase the velocity of development cycles, where much of an application remains untouched and therefore wouldn’t require deployments.

Deployment schedules for a monolithic application can drive companies to take longer to release new features or incorporate bug fixes from fear of deploying a large application frequently. However, deploying a smaller microservice can provide freedom as deployment cycles can happen more quickly and often.

Expand Scalability Options

Independent scaling issues can be a key driver of the extraction to PHP microservices. Extracting portions of an application, allowing precise scaling for only the necessary components versus the entire application, facilitates easier and faster scaling. By pulling an often-used feature into its own service, it can enable a queue to leverage the functionality without firing the entire application for a specific request.

Learn More About Scaling PHP

Improve PHP App Maintainability

Application stability enhancements through microservices become beneficial, particularly where applications tend to experience unplanned bugs and downtime after deployments. Large applications, with many sets of hands touching the code, are difficult to coordinate. By migrating to microservices, it can be easier to plan precise regression testing with a reduced surface area.

Building the deployment package for an entire monolithic application can include many dependencies, each with its own dependencies. Building a deployment for a small and nimble microservice usually requires a much smaller build process, and therefore, can be more stable.

Learn More About PHP Dependency Management

Meet Cloud-Native or Containerization Goals

Resource dependency is another consideration for extraction to a microservice, as some components of an application may consume varying degrees of load compared to others. Rather than vertically scaling an entire application, it is more cost-effective to scale only the components experiencing the heaviest load. Through this, elasticity is also elevated as these portions can also be reduced when the load is no longer heavy.

Utilizing cloud resources and containerization, it becomes much easier to construct additional resources on the fly, especially with infrastructure as code practices. And likewise, it is similarly easy to destroy resources when they are no longer needed. With less reliance on hardware, applications can grow and shrink without concern or added cost and planning.

On-Demand Webinar: Managing Mission-Critical Web App Migrations

Watch along as Zend Senior Professional Services Engineer Clark Everetts dives into how to successfully manage mission-critical web app migrations.

Key Considerations Before Migrating to PHP Microservices

Despite the many benefits that can come from migrating from a PHP monolith to microservices, you should not rush into the decision. Instead, carefully evaluate your application's complexity, infrastructure, dependencies, and codebase. While this list is by no means exhaustive, the following considerations can help as you begin to create your plan.

Be Mindful of Lift-And-Shift Approaches

When transitioning from a PHP monolith to microservices, it might be tempting to adopt a lift-and-shift approach, which is migrating the monolithic application as-is to microservices. While this method may seem like a quick win, it often leads to performance bottlenecks and missed opportunities to fully leverage the benefits of microservices.

Instead, consider refactoring your application as part of the migration process. Refactoring allows you to redesign components to align with microservices principles, such as loose coupling and independent scalability. This approach ensures that your application can take full advantage of a cloud-native architecture, including faster release cycles, improved scalability, and the flexibility to experiment with new technologies.

However, refactoring comes with its own challenges, such as increased complexity and the need for comprehensive testing. To mitigate these risks, adopt an incremental migration strategy and gradually replace monolithic components with microservices. This will ensure minimal disruption to the application and user experience.

Application Complexity

As applications grow and mature into full-featured solutions that serve business needs, they can become very complex. These complexities include the infrastructure required to support connectivity to databases, queues, and even other applications. Similarly, the code itself can consist of many intricacies in areas of cross-cutting concerns, as well as complex business logic. When dependencies on other software packages are added to the mix, complicating building and deployment, a codebase can become messy and ridden with race conditions and/or memory leaks.

Growth of an application can take years to reach a point of feature completeness, and during that time, technology continually changes with more advanced methods to achieve solutions. These changes to meet advancement also affect a codebase in ways that cannot be measured until the condition of the code is unwieldy.

In situations where the application has grown to this stage, migrating to microservices is the least expensive, and sometimes the only, method to ensure the continuation of the business.

Infrastructure Readiness

A large concern in regard to legacy applications is how they can hinder the velocity at which a company can pivot to meet the needs of customers. With a large monolithic application and the demands placed upon engineers in terms of development time, deployment complexities, and strategic planning, an organization’s capacity to take on new projects for continued growth is severely threatened.

Migrating from a PHP monolith to microservices may allow a company the freedom to consider new technologies, varying logistics, missing skillsets, advanced infrastructure, and operational processes they may have been missing.

Learn More About Modernizing Legacy Applications in PHP

Data Management Plans

Data can become an important topic, requiring planning and attention, as an application grows. Large applications typically generate huge amounts of metadata, temporary storage, databases, and queues. Each type of data and data location should have a data management plan for the data creation, storage, sharing, preservation, and destruction.

Moving your application from a PHP monolith to microservices can make data management easier through the same management tools to be used for deployment, as well as being cleaned up as temporary infrastructure is scaled up or down with the application.

Similarly, the area of data description benefits from the possibility that data knowledge can be more precisely mapped and defined.

Timeline and Available Resources

Leveraging microservices can initially strain software engineering teams as they split into smaller teams and more targeted projects. Ultimately, as the team becomes more acclimated to supporting a microservice architecture, it will become easier to plan the resources required for projects. However, that takes education, planning, and time. 

Another common pitfall is time estimation with a new microservice mindset, as teams are introduced to the restricted scope of a microservice at a much smaller scale than the monolith. A microservice is more contained than the much larger complexities of the monolith, facilitating faster velocity and scope.

Available In-House PHP Expertise

Migrating to a microservices architecture requires careful planning and knowledge. Software engineers require added specialized training related to microservices to ensure the required decision points are handled and thought out. 

Unfortunately, it is not uncommon for companies to experience costly pitfalls stemming from a restricted knowledge base, as software engineers strive to deliver beyond their level of knowledge. It is not advisable to jump into PHP microservices without in-house expertise to map out the processes, resources, and tools for the project. Instead, it is better to contract with a trusted third-party, such as Zend, to complete your transition from a PHP monolith to microservices architecture.

Final Thoughts

Migrating from a PHP monolith to a microservices architecture can be a complex and resource-intensive process, but it doesn’t have to be overwhelming. Partnering with expert consultants like Zend can simplify the transition, ensuring a smooth and efficient migration. With our deep expertise in PHP and modern web application architecture, we can help you avoid common pitfalls, optimize mission-critical apps, and accelerate your journey toward a scalable, maintainable, and future-ready application.

Zend Professional Services Handles the Heavy Lifting

The Zend team tackles the toughest problems in PHP, such as migrating to a microservices architecture, while you focus on driving innovation and growth. Explore our service options or contact us today to discuss the specifics of your infrastructure.

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Additional Resources

• On-Demand Webinar - How to Modernize Legacy Web Apps
• On-Demand Webinar - Optimizing PHP Apps: Strategies to Gain a Competitive Edge
• White Paper - The Costs of Building PHP In House
• Blog - When to Rewrite vs. Refactor Your Web App
• Blog - Guide to Enterprise Web App Development
• Blog - When to Use a PHP Application Server