As I stated in the section that you just read, below I coded several hands-on examples that illustrate how the data validation system that you learned earlier works to check some basic input data.

Here are the mentioned examples, along with their corresponding outputs:

try{
   // create observer object
   $observer=new Observer;

   // create validator objects
   $alphaVal=new AlphaValidator;
   $numVal=new NumberValidator;
   $emailVal=new EmailValidator;

   // validate some basic input data
   $alphaVal->validate('This is a valid input string');
   $numVal->validate('This is not a number');
   $emailVal->validate('user@domain.com');
   if(!Observer::checkData()){
      echo 'Inputted data is not valid';
   }
   else{
      echo 'Inputted data is valid';
   }

   // displays the following:
   // Inputted data is not valid
}
catch(Exception $e){
   echo $e->getMessage();
   exit();
}

//*******************************************
try{
   // create observer object
   $observer=new Observer;

   // create validator objects
   $alphaVal=new AlphaValidator;
   $numVal=new NumberValidator;
   $emailVal=new EmailValidator;

   // validate some basic input data
   $alphaVal->validate('This is a valid input string');
   $numVal->validate(1);
   $emailVal->validate('user@domain');
   if(!Observer::checkData()){
      echo 'Inputted data is not valid';
   }
   else{
      echo 'Inputted data is valid';
   }

   // displays the following:
   // Inputted data is not valid
}
catch(Exception $e){
   echo $e->getMessage();
   exit();
}

//*******************************************
try{
   // create observer object
   $observer=new Observer;

   // create validator objects
   $alphaVal=new AlphaValidator;
   $numVal=new NumberValidator;
   $emailVal=new EmailValidator;

   // validate some basic input data
   $alphaVal->validate('1 is a number');
   $numVal->validate(1234);
   $emailVal->validate('user@domain.com');
   if(!Observer::checkData()){
      echo 'Inputted data is not valid';
   }
   else{
      echo 'Inputted data is valid';
   }

   // displays the following:
   // Inputted data is not valid
}
catch(Exception $e){
   echo $e->getMessage();
   exit();
}

//*******************************************
try{
   // create observer object
   $observer=new Observer;

   // create validator objects
   $alphaVal=new AlphaValidator;
   $numVal=new NumberValidator;
   $emailVal=new EmailValidator;

   // validate some basic input data
   $alphaVal->validate('S');
   $numVal->validate(1234);
   $emailVal->validate('user@domain.com');
   if(!Observer::checkData()){
      echo 'Inputted data is not valid';
   }
   else{
      echo 'Inputted data is valid';
   }

   // displays the following:
   // Inputted data is valid
}
catch(Exception $e){
   echo $e->getMessage();
   exit();
}

Weren't all the above code samples easy to follow? I'm sure they were. As you can see, the previous data checking mechanism uses the programmatic model imposed by the observer pattern, along with a single static property to validate different types of inputted data. Considering that coding the prior classes may take only a few minutes, and the system's capacity to be expanded upon, you'll have to agree with me that using static properties and methods with PHP 5 brings many benefits. 

Final thoughts

Sadly, we've come to the end of this series. Hopefully, after reading all these tutorials, you'll be better prepared to start using static data with your own PHP-driven applications.

See you in the next PHP tutorial!