NextIteratorCallbackIterator.php

<?php

function main() {
	
	$limit = 100;
	$offset = 0;
	
	$iter = new NextIteratorCallbackIterator(function() use ($orm, $limit, &$offset) {
		printf("selecting next bunch at offset %d\n", $offset);
		$recs = $orm->select($filter, $sorting, $limit , $offset);
		$offset += $limit;
		if ($recs) {
			return new ArrayIterator($recs);
		}
		return null; // end reached
	});

	$i=0;
	foreach ($iter as $key => $value) {
		printf("%20s : %-20s\n", $key, $value);
		if (++$i>1000) break; // just to prevent an infinit loop during development
	}
	
}



class NextIteratorCallbackIterator implements Iterator {
	private $_iterator = null;
	private $_count = 0;
	private $_callback;
	
	public function __construct($callback) {
		if (!is_callable($callback)) {
			throw new Exception(__CLASS__.": callback must be callable");
		}
		$this->_callback = $callback;
	}
	
	public function current() {
		return $this->_iterator !== null ? $this->_iterator->current() : null;
	}
	
	public function key() {
		return $this->_iterator !== null ? $this->_iterator->key() : null;
	}
	
	public function next() {
		$tryNext = ($this->_iterator === null);
		do {
			if ($tryNext) {
				$tryNext = false;
				$this->_iterator = call_user_func($this->_callback, ++$this->_count);
			}
			elseif ($this->_iterator !== null) {
				$this->_iterator->next();
				if ($this->_iterator->valid() == false) {
					$tryNext = true;
				}
			}
		} while ($tryNext);
	}
	
	public function rewind() {
		$this->_iterator = call_user_func($this->_callback, $this->_count = 0);
	}
	
	public function valid () {
		return $this->_iterator !== null;
	}
}

main();