Kombinationen.php

<?php

function recursiveCombinatorics($strings, $removed , &$combinations, $recursionLevel, $debug) {
	$rec = str_repeat('&nbsp;', 8*$recursionLevel);
	
	foreach($strings as $i => $string) {
		if($debug) printf("%srecursiveCombinatorics(strings=array(%s), removed=array(%s), combinations=array(%s))<br>",
			$rec,
			implode(', ', $strings),
			implode(', ', $removed),
			implode(', ', array_keys($combinations))
		);
		
		// recursive argument
		$recRemoved = array_merge($removed, array($string));
		$recStrings = $strings;
		unset($recStrings[$i]);
		
		// (recursive) check for combinations
		sort($recRemoved);
		$combination = implode('-', $recRemoved);
		if(!isset($combinations[$combination])) {
			$combinations[$combination] = 0;
			
			if(count($recStrings) > 0) {
				recursiveCombinatorics($recStrings, $recRemoved, $combinations, ++$recursionLevel, $debug);
				$recursionLevel--;
			}
		}
	}
}

// Kombinationen suchen
$strings = array('01', '03', '02', '04');
$combinations = array();
recursiveCombinatorics($strings, array(), $combinations, 0, false);

// Ausgeben
ksort($combinations);
foreach($combinations as $combination => $devNull)
	echo "$combination<br>";