Making forms object-oriented Page 7

Example of a form

Now we are equipped for the final touch: building a small example. I will demonstrate
creation of the first page of a wizard that should collect some information. Let’s
say, about a subscription to some internet resource. As the first step,
the user must enter the username he is going to use, correct email address and select
type of the registration. Based on the registration type user chooses,
the wizard
should proceed to a corresponding screen. Before the wizard can proceed, it validates
values that the user enters. I will not build the forms for the second step. There’s
not much interesting to do without introducing additional input
classes; and I would still like the article’s subject to stay in the center of
discussion.

<?php
  define('MinNameLength', 5);
  class RegForm01 extends FormProcessor {
    function CustomCheck() {
      if (strlen($this->Values['Name']) < MinNameLength)
        $this->Errors['Name'] = 
            'Username should contain at least ' . MinNameLength . ' symbols';
      if ($this->Values['Email']) {
        if (!eregi('^[-!#$%&'*+./0-9=?A-Z^_`a-z{|}~]+
            @[-!#$%&'*+/0-9=?A-Z^_`a-z{|}~]+.[-!#$%&'*+
            './0-9=?A-Z^_`a-z{|}~]+$', $this->Values['Email']))
          $this->Errors['Email'] = 'Value entered does not 
            appear to be a valid e-mail address';
      } else {
        $this->Errors['Email'] = 
            'E-mail address is required to complete subscription';
      }
    }
    function NextWizardPage() {
      //decision about what wizard's screen to load next is made here,
      //based on the submitted values:
      return ($this->Values['PaymentMethod'] == 
        'P')?'reg_form_free.php':'reg_form_payed.php';
    }
    function StoreData() {
      // we will not discuss storing persistent variables in this article.
      // here would normally appear code that updates a database or
      // stores session variables
      STORE_VARIABLE($this->Values['Name']);
    }
    function DisplayForm() {
    // I'm not sure you meet a form like this on a real web-site =), but I hope
    // it'll do for the example
?>

<form action="<?php echo $PHP_SELF?>" method="POST">
    Username: <?php new TextInput($this, 'Name', '', 'size="30" maxlength="100"')?>
    <?php $this->ErrorReport('Name')?>

    Email: <?php new TextInput($this, 'Email', '', 'size="30" maxlength="100"')?>
    <?php $this->ErrorReport('Email')?>
    <br><br>
    Subscription type:<br>
    <?php new RadioButtons($this, 'SubscrType', array('P'=>'Preview', 'M'=>'Membership'), 'P')?>
    <?php $this->ErrorReport('SubscrType')?>
    <br>
    <br>
    <?php $this->Additional()?>
    <input type="submit" name="Submit" value="Submit">
</form>

<?php
    }
  }
  $form = new RegForm01('RegForm01', 'reg_form01.php');
?>

This code can also be downloaded from
here.

Conclusion

Object-oriented programming is an efficient and powerful technique. It allows
one to create reusable, easily adjustable components that make programming process
fast and, honestly, very much fun, too. I hope, my little experience that I
presented here will inspire you to build your own libraries of classes that
would be a basement for complex and sophisticated web applications.

— Yuri