<?php
class Formm
{
    protected $sAction;
    
    protected $sMethod;
    
    protected $aElements = array();
    
    public function __construct($sAction, $sMethod = 'post')
    {
        $this->sAction = $sAction;
        $this->sMethod = $sMethod;
    }
    
    public function addElement(FormElement $oElement)
    {
        $this->aElements[] = $oElement;
    }
    
    public function render()
    {
        foreach ($this->aElements as $oElement)
        {
            $sElements .= $oElement->render() . "\\r\
";
        }
        return sprintf(
            '<form action="&#37;s" method="%s">
                %s
            </form>',
            $this->sAction,
            $this->sMethod,
            $sElements
        );
    }
}

abstract class FormElement
{
    protected $aAttributes;
    
    public function addAttribute($sName, $mValue)
    {
        $this->aAttributes[$sName] = $mValue;
    }
    
    abstract public function render();
}

class TextFormElement extends FormElement
{
    public function render()
    {
        foreach ($this->aAttributes as $sName => $mValue)
        {
            $sAttributes .= sprintf('%s="%s" ', $sName, $mValue);
        }
        return sprintf(
            '<input type="text" %s/>',
            $sAttributes
        );
    }
}

class PasswordFormElement extends FormElement
{
    public function render()
    {
        foreach ($this->aAttributes as $sName => $mValue)
        {
            $sAttributes .= sprintf('%s="%s" ', $sName, $mValue);
        }
        return sprintf(
            '<input type="password" %s/>',
            $sAttributes
        );
    }
}

class SubmitFormElement extends FormElement
{
    public function render()
    {
        foreach ($this->aAttributes as $sName => $mValue)
        {
            $sAttributes .= sprintf('%s="%s" ', $sName, $mValue);
        }
        return sprintf(
            '<input type="submit" %s/>',
            $sAttributes
        );
    }
}

$oForm = new Form('/users/login/');

$oUsernameField = new TextFormElement();
$oUsernameField->addAttribute('name', 'username');

$oPasswordField = new PasswordFormElement();
$oPasswordField->addAttribute('name', 'password');

$oSubmitButton = new SubmitFormElement();
$oSubmitButton->addAttribute('name', 'submit');
$oSubmitButton->addAttribute('value', 'login');

$oForm->addElement($oUsernameField);
$oForm->addElement($oPasswordField);
$oForm->addElement($oSubmitButton);
echo $oForm->render();
/*
<form action="/users/login/" method="post">
    <input type="text" name="username" />
    <input type="password" name="password" />
    <input type="submit" name="submit" value="login" />
</form>
*/
?>