Listing all the classes required to implement the strategy pattern - PHP

The strategy design pattern is applied much more often than you might think, so if you want to find out how to implement it with PHP 5, this article should guide you through the whole learning process. Welcome to the final installment of the series that began with “Introducing the Strategy Pattern.” In two parts, this series walks you through the key points of how the strategy pattern works, and accompanies its theoretical concepts with copious hands-on examples.

TABLE OF CONTENTS:

By: Alejandro Gervasio

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March 06, 2007

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As I promised before, here are all the classes that I built over the course of this tutorial to apply the strategy pattern with PHP 5:

// define 'ValidationStrategySelector' class
class ValidationStrategySelector{
   private $strategy=NULL;
   public function __construct($strategy){
     if($strategy!='alpha'&&$strategy!='alphanum'&&$strategy!
='number'&&$strategy!='email'){
       throw new Exception('Invalid parameter for validation
strategy!');
     }
     switch($strategy){
       case "alpha":
       $this->strategy=new StrategyAlphabetic();
         break;
       case "alphanum":
         $this->strategy=new StrategyAlphanumeric();
         break;
       case "number":
         $this->strategy=new StrategyNumber();
         break;
       case "email":
         $this->strategy=new StrategyEmail();
         break;
     }
   }
   public function validateData($inputData){
     if(!$this->strategy->validateData($inputData)){
       return 'Input data is not valid!';
     }
   return 'Input data is OK!';
   }
}
// define 'StrategyAlphabetic' class
class StrategyAlphabetic{
   public function validateData($inputData){
     if(!$inputData||!preg_match("/^[a-zA-Z]+$/",$inputData)){
       return false;
     }
     return true;
   }
}
// define 'StrategyAlphanumeric' class
class StrategyAlphanumeric{
   public function validateData($inputData){
     if(!$inputData||!preg_match("/^[a-zA-Z0-9]+$/",$inputData)){
       return false;
     }
     return true;
   }
}
// define 'StrategyNumber' class
class StrategyNumber{
   public function validateData($inputData){
     if(!$inputData||!is_numeric($inputData)){
       return false;
     }
     return true;
   }
}
// define 'StrategyEmail' class
class StrategyEmail{
   public function validateData($inputData){
     if(!$inputData||!preg_match("/.+@.+..+./",$inputData)||!
checkdnsrr(array_pop(explode("@",$inputData)),"MX")){
       return false;
     }
     return true;
   }
}

That's it. As usual with all my articles, feel free to modify the signature of all the classes that I showed here so you can acquire a better understanding of this pattern. Have a good time!

Final thoughts

Unfortunately, we've come to the end of this series. However, I hope that after reading these two articles, you'll have a better idea not only of how the strategy pattern works, but how it can be used in real situations.

See you in the next PHP tutorial!