Provide implementation for abstract class in PHP

//  w  w w .  j a v a 2 s.  c  o  m
<?php

abstract class Shape {
  private $_color = "black";
  private $_filled = false;

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

  public function setColor( $color ) {
    $this->_color = $color;
  }

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

  public function fill() {
    $this->_filled = true;
  }

  public function makeHollow() {
    $this->_filled = false;
  }

  abstract public function getArea();
}

class Circle extends Shape {
  private $_radius = 0;

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

  public function setRadius( $radius ) {
    $this->_radius = $radius;
  }

  public function getArea() {
    return M_PI * pow( $this->_radius, 2 );
  }
}

class Square extends Shape {
  private $_sideLength = 0;

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

  public function setSideLength( $length ) {
    $this->_sideLength = $length;
  }

  public function getArea() {
    return pow( $this->_sideLength, 2 );
  }
}

class Rectangle extends Shape {
  private $_width = 0;
  private $_height = 0;

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

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

  public function setWidth( $width ) {
    $this->_width = $width;
  }

  public function setHeight( $height ) {
    $this->_height = $height;
  }

  public function getArea() {
    return $this->_width * $this->_height;
  }
}


class ShapeInfo {
  private $_shape;

  public function setShape( $shape ) {
    $this->_shape = $shape;
  }

  public function showInfo( ) {
    echo "<p>The shape's color is " . $this->_shape->getColor();
    echo ", and its area is " . $this->_shape->getArea() .".</p>";
  }
}


$myCircle = new Circle;
$myCircle->setColor( "red" );
$myCircle->fill();
$myCircle->setRadius( 4 );

$mySquare = new Square;
$mySquare->setColor( "green" );
$mySquare->makeHollow();
$mySquare->setSideLength( 3 );

$info = new ShapeInfo();

$info->setShape( $myCircle );
$info->showInfo();
$info->setShape( $mySquare );
$info->showInfo();

$myRect = new Rectangle;
$myRect->setColor( "yellow" );
$myRect->fill();
$myRect->setWidth( 4 );
$myRect->setHeight( 5 );

$info->setShape( $myRect );
$info->showInfo();

?>