<?PHP 
class GraphicsEnvironment 
{ 
  public $width; 
  public $height; 
  public $gdo; 
  public $colors = array(); 

  public function __construct( $width, $height ) 
  { 
    $this->width = $width; 
    $this->height = $height; 
    $this->gdo = imagecreatetruecolor( $width, $height ); 
    $this->addColor( "white", 255, 255, 255 ); 
    imagefilledrectangle( $this->gdo, 0, 0, 
      $width, $height, 
      $this->getColor( "white" ) ); 
  } 

  public function width() { return $this->width; } 

  public function height() { return $this->height; } 

  public function addColor( $name, $r, $g, $b ) 
  { 
    $this->colors[ $name ] = imagecolorallocate( 
      $this->gdo, 
      $r, $g, $b ); 
  } 

  public function getGraphicObject() 
  { 
    return $this->gdo; 
  } 

  public function getColor( $name ) 
  { 
    return $this->colors[ $name ]; 
  } 

  public function saveASPng( $filename ) 
  { 
    imagepng( $this->gdo, $filename ); 
  } 
} 

abstract class GraphicsObject 
{ 
  abstract public function render( $ge ); 
  abstract public function z(); 
} 

abstract class BoxObject extends GraphicsObject 
{ 
  protected $color; 
  protected $sx; 
  protected $sy; 
  protected $ex; 
  protected $ey; 
  protected $z; 

  public function __construct( $z, $color, $sx, $sy, $ex, $ey ) 
  { 
    $this->z = $z; 
    $this->color = $color; 
    $this->sx = $sx; 
    $this->sy = $sy; 
    $this->ex = $ex; 
    $this->ey = $ey; 
  } 

  public function z() { return $this->z; } 
} 

class Line extends BoxObject 
{ 
  public function render( $ge ) 
  { 
    imageline( $ge->getGraphicObject(), 
      $this->sx, $this->sy, 
      $this->ex, $this->ey, 
      $ge->getColor( $this->color ) ); 
  } 
} 

class Rectangle extends BoxObject 
{ 
  public function render( $ge ) 
  { 
    imagefilledrectangle( $ge->getGraphicObject(), 
      $this->sx, $this->sy, 
      $this->ex, $this->ey, 
      $ge->getColor( $this->color ) ); 
  } 
} 

class Oval extends BoxObject 
{ 
  public function render( $ge ) 
  { 
    $w = $this->ex - $this->sx; 
    $h = $this->ey - $this->sy; 
    imagefilledellipse( $ge->getGraphicObject(), 
      $this->sx + ( $w / 2 ), 
      $this->sy + ( $h / 2 ), 
      $w, $h, 
      $ge->getColor( $this->color ) ); 
  } 
} 
?> 

 
<?php 
require_once( "glib.php" ); 

function zsort( $a, $b ) 
{ 
  if ( $a->z() < $b->z() ) return -1; 
  if ( $a->z() > $b->z() ) return 1; 
  return 0; 
} 

$ge = new GraphicsEnvironment( 400, 400 ); 

$ge->addColor( "black", 0, 0, 0 ); 
$ge->addColor( "red", 255, 0, 0 ); 
$ge->addColor( "green", 0, 255, 0 ); 
$ge->addColor( "blue", 0, 0, 255 ); 

$gobjs = array(); 
$gobjs []= new Oval( 100, "red", 50, 50, 150, 150 ); 
$gobjs []= new Rectangle( 200, "black", 100, 100, 300, 300 ); 

usort( $gobjs, "zsort" ); 

foreach( $gobjs as $gobj ) { $gobj->render( $ge ); } 

$ge->saveAsPng( "test.png" ); 
?> 

 
$gobjs []= new Oval( 200, "red", 50, 50, 150, 150 ); 
$gobjs []= new Rectangle( 100, "black", 100, 100, 300, 300 ); 

 
function zsort( $a, $b ) 
{ 
  if ( $a->z() < $b->z() ) return -1; 
  if ( $a->z() > $b->z() ) return 1; 
  return 0; 
} 

class Group extends GraphicsObject 
{ 
  private $z; 
  protected $members = array(); 
  public function __construct( $z ) 
  { 
    $this->z = $z; 
  } 
  public function add( $member ) 
  { 
    $this->members []= $member; 
  } 
  public function render( $ge ) 
  { 
    usort( $this->members, "zsort" ); 
    foreach( $this->members as $gobj ) 
    { 
      $gobj->render( $ge ); 
    } 
  } 
  public function z() { return $this->z; } 
} 

 
<?php 
require_once( "glib.php" ); 

$ge = new GraphicsEnvironment( 400, 400 ); 

$ge->addColor( "black", 0, 0, 0 ); 
$ge->addColor( "red", 255, 0, 0 ); 
$ge->addColor( "green", 0, 255, 0 ); 
$ge->addColor( "blue", 0, 0, 255 ); 

$g1 = new Group( 0 ); 
$g1->add( new Oval( 200, "red", 50, 50, 150, 150 ) );   
$g1->add( new Rectangle( 100, "black", 100, 100, 300, 300 ) ); 

$g1->render( $ge ); 

$ge->saveAsPng( "test.png" ); 
?>