Extending isset() and empty() functionality and the new is_recursively_set() for checking recursively an array with several keys of depth.

isset_empty_extended.php

<?php
/**
 * Usage:
 *
 * Instead of:
 *	if(isset($array['element1']) && isset($array['element2']) && isset($array['element3']) && isset($array['element4'] && isset($array['element5']))
 *
 * Use:
 *	if(is_set_in($array, 'element1', 'element2', 'element3', 'element4', 'element5'))
 *
 * Conclusion: Cleaner and legible.
 * The function is_empty_in() also checks the value with empty() for each element.
 */
 
function is_set_in()
{
	$args = func_get_args();

	if(!isset($args[0]) || !isset($args[1]))
		return null;
	
	$array = array_shift($args);
	
	foreach($args as $arg)
	{
		if(!isset($array[$arg]))
			return false;
	}
	return true;
}

function is_not_set_in()
{
	$args = func_get_args();

	if(!isset($args[0]) || !isset($args[1]))
		return null;
	
	$array = array_shift($args);
	
	foreach($args as $arg)
	{
		if(isset($array[$arg]))
			return false;
	}
	return true;
}

function is_empty_in()
{
	$args = func_get_args();

	if(!isset($args[0]) || !isset($args[1]))
		return null;
	
	$array = array_shift($args);
	
	foreach($args as $arg)
	{
		if(!isset($array[$arg]) || !empty($array[$arg]))
			return false;
	}
	return true;
}

function is_not_empty_in()
{
	$args = func_get_args();

	if(!isset($args[0]) || !isset($args[1]))
		return null;
	
	$array = array_shift($args);
	
	foreach($args as $arg)
	{
		if(!isset($array[$arg]) || empty($array[$arg]))
			return false;
	}
	return true;
}
/**
 * Usage of is_recursively_set($array, $keys = array()):
 *
 * Instead of:
 *	if(isset($array['element1']) && isset($array['element1']['element2']) && isset($array['element1']['element2']['element3']))
 *
 * Use:
 *	if(is_set_in($array, array('element1', 'element2', 'element3')))
 *
 * Conclusion: Again, cleaner and legible.
 */
function is_recursively_set($array, array $keys = array())
{
	if(!is_array($array))
		return true;

	if(!isset($array[$keys[0]]))
		return false;
	
	$key = array_shift($keys);

	return is_recursively_set($array[$key], $keys);
}