DRY Principle in PHP

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In the realm of software development, the DRY (Don’t Repeat Yourself) principle serves as a guiding light, illuminating the path to code efficiency and maintainability. DRY advocates for the elimination of code duplication, as redundant code can lead to errors, inconsistencies, and complex maintenance.

In this article, we’ll explore the DRY principle in the context of a PHP-based file managing example, showcasing how adhering to DRY can lead to more streamlined and maintainable code.

Unveiling the DRY Principle

To comprehend the DRY principle, we must first grasp its core tenets:

  1. Code Duplication: DRY discourages the replication of code in multiple places within a codebase, as it can result in inconsistencies and maintenance challenges.
  2. Modularization: It encourages developers to create reusable modules and functions, facilitating code organization and reusability.
  3. Single Source of Truth: DRY advocates for having a single, authoritative representation of specific code or data, rather than multiple copies scattered across an application.

Recognizing Code Duplication in a File Manager

Consider the scenario of building a PHP-based File Manager, a common task in web applications. In such an application, various operations like file uploads, deletions, and retrievals are performed. However, without adhering to DRY, code duplication can easily creep in.

Here’s an example of duplicated code for file deletion:

public function archiveInvoice($id) {    
  $deletedCounter = 0;
  $proForma = ProFormInvoice::get($id);
  
  if (file_exists($proForma->path)) {
        unlink($proForma->path);
    	$deletedCounter++;
  }
  
  $invoice = Invoice::get($id);
  
  if (file_exists($invoice->path)) {
        unlink($invoice->path);
    	$deletedCounter++;
  } 
  
  return $deletedCounter;  
}

In this scenario, we have repeated the if and unlink() function for multiple files, a clear violation of the DRY principle. To embrace the DRY principle, we can create a reusable function for file deletion:

public function archiveInvoice($id) {  
  
  $deletedCounter = 0;
  
  $proForma = ProFormInvoice::get($id);
  $archivedCount += (int)deleteFile($proForma->path);
    
  $invoice = Invoice::get($id);
  $archivedCount += (int)deleteFile($invoice->path);
  
  return $deletedCounter;
}

function deleteFile($filePath)
{
    if (file_exists($filePath)) {
        unlink($filePath);
        return true;
    }
  
    return false;
}

By encapsulating the file deletion logic within the deleteFile() function, we centralize the code for this operation. This not only eliminates redundancy but also makes the code more maintainable, as changes to the file deletion process can be made in a single location.

Benefits of DRY

The application of the DRY principle in our File Manager example yields several benefits:

  • Code Reusability: The deleteFile() function can be used throughout the application whenever file deletions are required.
  • Maintainability: Changes or improvements to the file deletion process can be made in one place, reducing the risk of errors and ensuring consistency.
  • Readability: Code becomes more readable, as complex operations are abstracted into well-named functions.

Conclusion

The DRY principle, a cornerstone of software development, urges us to eliminate code duplication and foster code efficiency and maintainability.

In your own PHP projects, remember the DRY principle: Don’t Repeat Yourself. By doing so, you’ll create code that is more efficient, easier to understand, and simpler to maintain, ultimately saving time and effort.

Also, take in mind that there are more principles one should follow. Take a look at The KISS Principle with PHP Examples or start going through SOLID principles from the Single Responsibility Principle (SRP).

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