<?php

class AlphabetIterator extends FilterIterator
{
	private
		$letter;

	function __construct(array $array, $letter)
	{
		parent::__construct(new ArrayIterator($array));
		$this -> letter = $letter;
	}
	
	function accept()
	{
		$current = $this -> current();
		return strlen($current) && ($current[0] === $this -> letter);
	}
}

$list = array('alpha', 'beta', 'bar', 'baz', 'foo', 'blaz');
$list = new IteratorIterator(new AlphabetIterator($list, 'b'));

foreach($list as $word)
{
	echo $word;
}

?>