Composite Design Pattern

Composite.php

<?php

abstract class SongComposite{
	public function songInfo(){}
}
class Song extends SongComposite{
	private $songTitle;
	private $songBand;
	public function __construct($sTitle, $sBand){
		$this->songTitle = $sTitle;
		$this->songBand = $sBand;
	}
	public function songInfo(){
		return "Title: ".$this->songTitle."\r\n"."Band: ".$this->songBand."\r\n";
	}
}
class SongGroup extends SongComposite{
	private $Songs = array();
	private $songCount;
	public function __construct(){
		$this->songCount = 0;
	}
	public function addSong(SongComposite $s){
		array_push($this->Songs,$s);
		$this->songCount++;
	}
	public function removeSong($index){
		$index = $index--; //To match the array index
		if($index > $this->songCount){
			echo $this->songCount;
			return;
		}
			
		unset($this->Songs[$index]);
		$this->songCount--;
		
	}
	public function songInfo(){
		echo "\r\n";
		foreach ($this->Songs as $Song) {
			echo $Song->songInfo();
			echo "\r\n";
		}
	}	
}
$song1 = new Song("Heart of Steel","Manowar");
$song2 = new Song("Master of puppets","Metalica");
$song3 = new Song("Emerald Sword","Rhapsody");
$SongGroup = new SongGroup();
$SongGroup->addSong($song1);
$SongGroup->addSong($song2);
$SongGroup->addSong($song3);
$SongGroup->songInfo();
$SongGroup->removeSong(2);
echo "=============== After remove ==================\r\n";
$SongGroup->songInfo();
?>