Service Layer in PHP

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Service Layer in PHP

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Service Layer in PHP

• Service Layer is a list of service classes that
  are used to handle application logic. Service
  classes are distinguished from used from
  different front ends.
• At every level of abstraction, Source code is
  used to represent the data entities and their
  behavior. In object-oriented programming, there
  are different types of logic that can be
  partitioned into

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• Application logic It is the scope of a service
  layer and it is not domain-specific. For example,
  converting objects into JSON or XML is a function
  of application logic. It can even be used with
  application-specific classes. The task of showing
  data in a particular format is unobserved to the
  domain. As it is not domain-specific.
• Business logic It is encapsulated in a domain
  model. And it is specific to the particular
  domain the application works in. In an enterprise
  application, all added value depends on business
  logic.
• Presentation logic Presentation logic is
  considered as the subset of application logic.
  Which handled the end-user view of the
  application.

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• All those different aspects of an application are
  organized into different layers. Where each layer
  resides on the top of the previous layer. In
  older approaches, there is an infrastructure
  layer on which the business logic depends and
  which can deal with persistent issues.
• A Service Layer is useful when there are multiple
  front-ends to a common domain model. These
  interfaces or APIs delegate the application logic
  to the service layer. Which may encapsulate each
  other.
• Responsibility of Service Layer- It includes the
  responsibility of CRUD function(s) over the
  object of a specific domain model. Some of the
  responsibilities are already included while
  others are only specified as interfaces.

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Example code

• It includes two service classes one as the
  implementation of the interface of the domain
  model and another is only employed at a higher
  level
• lt?php
• require_once 'domain.php'
• /
• Adapter for an interface defined in the lower
  layer
• /

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• class EmailRepositoryClass implements
  EmailRepository
• public function getAllEmail(address)
• // fake implementation
• mail new Email()
• mail-gtsetSender(sunil_at_example.com')
• mail-gtsetRecipient(sunilseth9i_at_example.com')
• mail-gtsetSubject('testing')
• mail-gtsetText('it is just testing the class')
• return array(
• mail

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• )
• /
• Service that belongs only to the very Service
  Layer.
• It may have an interface, but it will be kept
  in this layer.
• /
• class EmailTransferService

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• /
• Transforming an object to XML is a common task
  for a Service Layer.
• However, dependencies towards the Domain Model
  are well-accepted
• but they don't mean that this layer's classes
  should be
• included in the lower layer.
• Keeping the XML transformation in one place
  aids different front-end
• /
• public function toXml(Email mail)

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• return "ltmailgt\n"
• . " ltsendergt" . mail-gtgetSender() .
  "lt/sendergt\n"
• . " ltrecipientgt" . mail-gtgetRecipient() .
  "lt/recipientgt\n"
• . " ltsubjectgt" . this-gt_encode(mail-gtgetSubject(
  )) . "lt/subjectgt\n"
• . " lttextgt" . this-gt_encode(mail-gtgetText()) .
  "lt/textgt\n"
• . "lt/mailgt\n"

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• protected function _encode(text)
• return htmlentities(text)
• // client code
• repository new EmailRepositoryClass()
• transferService new EmailTransferService()
• foreach (repository-gtgetAllEmail('bob_at_example.com
  ') as mail)
• echo transferService-gttoXml(mail)

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