Extending the scope of data validation: defining some additional data checking classes - PHP

As I mentioned before, I was planning to extend the validation capabilities of the application. So my next task is to code some new classes, aimed at checking alphabetic and alphanumeric values, along with email addresses. Please take a look at the classes listed below:

  // define AlphaValidator class
  class AlphaValidator extends DataValidator{
    public function __construct($formObserver){
        parent::__construct($formObserver);
    }
    // validate alphabetic field
    public function validate($field,$errorMessage){
        if(!isset($this->method[$field])||!preg_match("/^[a-zA-Z]
+$/",$this->method[$field])){
            $this->notifyObserver($errorMessage);
        }
    }
  }
  // define AlphanumValidator class
  class AlphanumValidator extends DataValidator{
    public function __construct($formObserver){
        parent::__construct($formObserver);
    }
    // validate alphanumeric data
    public function validate($field,$errorMessage){
        if(!isset($this->method[$field])||!preg_match("/^[a-zA-
Z0-9]+$/",$this->method[$field])){
            $this->notifyObserver($errorMessage);
        }
    }
  }
  // define EmailValidator class
  class EmailValidator extends DataValidator{
    public function __construct($formObserver){
        parent::__construct($formObserver);
    }
    // validate email
    public function validate($field,$errorMessage){
        if(!isset($this->method[$field])||!preg_match
("/.+@.+..+/",$this->method[$field])||!checkdnsrr(array_pop
(explode("@",$this->method[$field])),"MX")){
            $this->notifyObserver($errorMessage);
    }
  }
  // define EmailValidatorWin class (Windows systems)
  class EmailValidatorWin extends DataValidator{
    public function __construct($formObserver){
        parent::__construct($formObserver);
    }
    public function validate($field,$errorMessage){
        if(!isset($this->method[$field])||!preg_match
("/.+@.+..+/",$this->method[$field])||!$this->windnsrr(array_pop
(explode("@",$this->method[$field])),"MX"){
            $this->notifyObserver($errorMessage);
        }
    }
    // private method 'windnsrr()' for Windows systems
    private function windnsrr($hostName,$recType=''){
        if(!empty($hostName)){
            if($recType=='')$recType="MX";
            exec("nslookup -type=$recType $hostName",$result);
            foreach($result as $line){
                if(preg_match("/^$hostName/",$line)){
                    return true;
                }
            }
            return false;
        }
        return false;
    }
  }

As shown above, I defined an additional set of data checking classes, in order to extend the capabilities of the application. It’s easy to see how these new classes have been created, since they’re also sub classes of the base “DataValidator” class.

Of course, since I wish to expand the functionality of the whole application, I covered the validation of alphanumeric and alphabetic values, together with the verification of email addresses, in two flavors: Unix-based and Windows systems.

At this stage, I provided this data-checking application with a decent number of checking classes. These classes are not only independent, but also capable of notifying a core object of any errors that occurred during the checking process. Definitely, you’ll agree with me that I’m on the right track for implementing the Observer pattern with PHP 5. Don’t you feel a little happier?

But, let’s get serious now and jump into the next section, so you can see the full source code of all the data checking classes that I defined before. Just go ahead and keep on reading.