We fear modernizing legacy applications, or going API first. But it's not as futile as you might think. With modern PHP microframeworks geared toward middleware it can be a breeze. Now the truth: It is a terribly difficult task full of pitfalls. But I will share how to do it in a step-by-step method that makes it much more approachable, and enable you to be a super hero.

1. Putting Legacy to REST
with Middleware
By:
Adam Culp
Twitter: @adamculp

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Putting Legacy to REST with Middleware
●
About me
– DevRel and Tech Lead at Nexmo
– OSS Contributor
– PHP-Fig voting member (IBM i Toolkit)
– Organizer SoFloPHP (South Florida)
– Organizer SunshinePHP (Miami)
– Long distance (ultra) runner
– Judo Black Belt Instructor

3. 3
Putting Legacy to REST with Middleware
●
About me
– DevRel and Tech Lead at Nexmo
– OSS Contributor
– PHP-Fig voting member (IBM i Toolkit)
– Organizer SoFloPHP (South Florida)
– Organizer SunshinePHP (Miami)
– Long distance (ultra) runner
– Judo Black Belt Instructor
I am the
PHP Ninja!!!

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Putting Legacy to REST with Middleware
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Fan of iteration
– Pretty much everything requires iteration to do well:
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Long distance running
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Judo
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Development
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Evading project managers
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Refactoring!

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Refactoring Legacy Code
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What is “Legacy Code”?
– Is there a coding standard for your project?

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Refactoring Legacy Code
●
What is “Legacy Code”?
– Is there a coding standard for your project?
– Is code using OOP?

7. 7
Refactoring Legacy Code
●
What is “Legacy Code”?
– Is there a coding standard for your project?
– Is code using OOP?
– Is Composer used in your project?

8. 8
Refactoring Legacy Code
●
What is “Legacy Code”?
– Is there a coding standard for your project?
– Is code using OOP?
– Is Composer used in your project?
– Is the project using a framework?

9. 9
Refactoring Legacy Code
●
What is “Legacy Code”?
– Is there a coding standard for your project?
– Is code using OOP?
– Is Composer used in your project?
– Is the project using a framework?
– Are you unit testing?

10. 10
Refactoring Legacy Code
●
What is “Legacy Code”?
– Is there a coding standard for your project?
– Is code using OOP?
– Is Composer used in your project?
– Is the project using a framework?
– Are you unit testing?
– Does your project avoid NIH?

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Refactoring Legacy Code
●
What is “Legacy Code”?
– Is there a coding standard for your project?
– Is code using OOP?
– Is Composer used in your project?
– Is the project using a framework?
– Are you unit testing?
– Does your project avoid NIH?
If you can answer “No” to any of these,
you may be creating “Legacy Code”!!!

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Refactoring Legacy Code
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What is “legacy” really?
– According to https://en.wikipedia.org/wiki/Legacy_code
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“...no longer supported or manufactured...”
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“...code inserted into modern software for the purpose of maintaining
an older or previously supported feature...”
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“...supporting older file formats...”
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“...code may no longer work without changes...”
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“...code that no longer runs on a later version of a system, or requires
a compatibility layer to do so...”

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Putting Legacy to REST with Middleware
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Why Rewrite?
– Change technology (PHP to Javascript, Python, etc.)
– Code is REALLY bad
– If less expensive to rewrite versus refactor
– Little to no chance to lose business logic
– Desire a “different” application

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Putting Legacy to REST with Middleware
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API First!
– API is first class citizen

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Putting Legacy to REST with Middleware
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API First!
– API is first class citizen
– API comes first, then implementation

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Putting Legacy to REST with Middleware
●
API First!
– API is first class citizen
– API comes first, then implementation
– Development teams can work in parallel

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Putting Legacy to REST with Middleware
●
API First!
– API is first class citizen
– API comes first, then implementation
– Development teams can work in parallel
– Reduces cost of developing apps
●
Through re-use of business logic

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Putting Legacy to REST with Middleware
●
API First!
– API is first class citizen
– API comes first, then implementation
– Development teams can work in parallel
– Reduces cost of developing apps
●
Through re-use of business logic
– Faster time to market

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Putting Legacy to REST with Middleware
●
API First!
– API is first class citizen
– API comes first, then implementation
– Development teams can work in parallel
– Reduces cost of developing apps
●
Through re-use of business logic
– Faster time to market
– OpenAPI

20. 20
Putting Legacy to REST with Middleware
●
API First!
– API is first class citizen
– API comes first, then implementation
– Development teams can work in parallel
– Reduces cost of developing apps
●
Through re-use of business logic
– Faster time to market
– OpenAPI
– Reduces risk of failure

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Putting Legacy to REST with Middleware
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Modernization Methods

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Putting Legacy to REST with Middleware
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Modernization Methods
– #1 Total Rewrite
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Create entirely new app
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Build until complete
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Big BANG!

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Putting Legacy to REST with Middleware
●
Modernization Methods
– #1 Total Rewrite
●
Create entirely new app
●
Build until complete
●
Big BANG!

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Putting Legacy to REST with Middleware
●
Modernization Methods
– #1 Total Rewrite
●
Create entirely new app
●
Build until complete
●
Big BANG!
●
Pitfalls
– Constant “scope creep”
– Maintain 2 apps
– Expensive!

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Putting Legacy to REST with Middleware
●
Modernization Methods
– #1 Total Rewrite
●
Create entirely new app
●
Build until complete
●
Big BANG!
●
Pitfalls
– Constant “scope creep”
– Maintain 2 apps
– Expensive!
●
Benefits
– Clean slate
– Energy/Excitement
– Less business disruption

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Putting Legacy to REST with Middleware
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Modernization Methods (cont’d)
– #2 REST API Backend
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Build an API
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Use the API to drive logic and data

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Putting Legacy to REST with Middleware
●
Modernization Methods (cont’d)
– #2 REST API Backend
●
Build an API
●
Use the API to drive logic and data
●
Pitfalls
– Requires cleanup of objects first
– Longer time to get productive
– Very difficult for spaghetti apps

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Putting Legacy to REST with Middleware
●
Modernization Methods (cont’d)
– #2 REST API Backend
●
Build an API
●
Use the API to drive logic and data
●
Pitfalls
– Requires cleanup of objects first
– Longer time to get productive
– Very difficult for spaghetti apps
●
Benefits
– Cleans up data/business logic
– Shorter time to completion

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Putting Legacy to REST with Middleware
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Modernization Methods #2 (How-To)
– Create standalone REST API
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Add one module at a time

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Putting Legacy to REST with Middleware
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Modernization Methods #2 (How-To)
– Create standalone REST API
●
Add one module at a time
– Refactor the Legacy application to use API as Service/Model

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Putting Legacy to REST with Middleware
●
Modernization Methods #2 (How-To)
– Create standalone REST API
●
Add one module at a time
– Refactor the Legacy application to use API as Service/Model
– Eventually API First, w/ frontend application

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Putting Legacy to REST with Middleware
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Modernization Methods (cont’d)
– #3 Legacy Middleware
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New application (as with rewrite)
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In stages

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Putting Legacy to REST with Middleware
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Modernization Methods (cont’d)
– #3 Legacy Middleware
●
New application (as with rewrite)
●
In stages
●
Pitfalls
– Takes upfront planning
– Takes longer
– Overall, still creating 2 new apps
– Not API first until the end

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Putting Legacy to REST with Middleware
●
Modernization Methods (cont’d)
– #3 Legacy Middleware
●
New application (as with rewrite)
●
In stages
●
Pitfalls
– Takes more planning
– Takes longer
– Overall, still creating 2 new apps
– Not API first until the end
●
Benefits
– Can update/implement new frontend faster (duplicated)
– Spaghetti app easier to manage
– Less business impact
– Marketing “new” features regularly

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Putting Legacy to REST with Middleware
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Modernization Methods #3 (How-To)
– New sub-directory for new app

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Putting Legacy to REST with Middleware
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Modernization Methods #3 (How-To)
– New sub-directory for new app
– Create LegacyMiddleware, add it before FinalMiddleware

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Putting Legacy to REST with Middleware
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Modernization Methods #3 (How-To)
– New sub-directory for new app
– Create LegacyMiddleware, add it before FinalMiddleware
– Fix issues with routing and includes

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Putting Legacy to REST with Middleware
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Modernization Methods #3 (How-To)
– New sub-directory for new app
– Create LegacyMiddleware, add it before FinalMiddleware
– Fix issues with routing and includes
– Update doc_root to be new location
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Site working as it used to

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Putting Legacy to REST with Middleware
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Modernization Methods #3 (How-To)
– New sub-directory for new app
– Create LegacyMiddleware, add it before FinalMiddleware
– Fix issues with routing and includes
– Update doc_root to be new location
●
Site working as it used to
– Start creating new modules in new app

40. 40
Putting Legacy to REST with Middleware
●
Modernization Methods #3 (How-To)
– New sub-directory for new app
– Create LegacyMiddleware, add it before FinalMiddleware
– Fix issues with routing and includes
– Update doc_root to be new location
●
Site working as it used to
– Start creating new modules in new app
– LegacyMiddleware called less and less

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Putting Legacy to REST with Middleware
●
Modernization Methods #3 (How-To)
– New sub-directory for new app
– Create LegacyMiddleware, add it before FinalMiddleware
– Fix issues with routing and includes
– Update doc_root to be new location
●
Site working as it used to
– Start creating new modules in new app
– LegacyMiddleware called less and less
– Remove legacy app once all endpoints satisfied

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Putting Legacy to REST with Middleware
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What is “Middleware”?
– NEW? way to build multi-layers as tiered approach to execution
– “Software glue” - wikipedia
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Implement communication and input/output
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Popular in ‘80s to link newer applications to legacy systems

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Putting Legacy to REST with Middleware
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Frameworks!
– Expressive (Laminas Project, formerly Zend Framework)
– Slim PHP
– Most others:
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Laravel
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Symfony
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Etc.

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Putting Legacy to REST with Middleware
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Testing
– Always test prior to refactoring
– Then refactor
– Then test again
– Refactor tests as needed
– Repeat

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Putting Legacy to REST with Middleware
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Tools
– Source Control
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Allows easier rollback
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Allows collaboration
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Git makes branching easier

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Putting Legacy to REST with Middleware
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Tools (cont’d)
– CI/CD
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Makes updates across team seamless

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Putting Legacy to REST with Middleware
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Conclusion
– Middleware makes modernization easier
– Do it in stages
– Test all the things...often
– Teamwork
– Love iteration!

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Putting Legacy to REST with Middleware
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Go!
– Your turn!

49. ●
Thank you!
– Code: https://github.com/adamculp/
Adam Culp
https://beachcasts.com
https://geekyboy.com
https://rungeekradio.com
Twitter @adamculp
Questions?