按模板生成组合

<?php

ini_set('memory_limit','10000M');
function combinations($arrays, $i = 0) {
	if (!isset($arrays[$i])) {
		return array();
	}
	if ($i == count($arrays) - 1) {
		return $arrays[$i];
	}
	
	// 	get combinations from subsequent arrays
	    $tmp = combinations($arrays, $i + 1);
	
	$result = array();
	
	// 	concat each array from tmp with each element from $arrays[$i]
	    foreach ($arrays[$i] as $v) {
		foreach ($tmp as $t) {
			$result[] = is_array($t) ? 
			                array_merge(array($v), $t) :
			                array($v, $t);
		}
	}
	
	return $result;
}


/**
* Generate all the possible combinations among a set of nested arrays.
 *
 * @param array $data  The entrypoint array container.
 * @param array $all   The final container (used internally).
 * @param array $group The sub container (used internally).
 * @param mixed $val   The value to append (used internally).
 * @param int   $i     The key index (used internally).
 */
 function generate_combinations(array $data, array &$all = array(), array $group = array(), $value = null, $i = 0)
 {
	$keys = array_keys($data);
	if (isset($value) === true) {
		array_push($group, $value);
	}
	
	if ($i >= count($data)) {
		array_push($all, $group);
	}
	else {
		$currentKey     = $keys[$i];
		$currentElement = $data[$currentKey];
		foreach ($currentElement as $val) {
			generate_combinations($data, $all, $group, $val, $i + 1);
		}
	}
	
	return $all;
}

function cartesian_product($a) {
	$result = array(array());
	foreach ($a as $list) {
		$_tmp = array();
		foreach ($result as $result_item) {
			foreach ($list as $list_item) {
				$_tmp[] = array_merge($result_item, array($list_item));
			}
		}
		$result = $_tmp;
	}
	return $result;
}

function get_combinations($arrays) {
	$result = array(array());
	foreach ($arrays as $property => $property_values) {
		$tmp = array();
		foreach ($result as $result_item) {
			foreach ($property_values as $property_value) {
				$tmp[] = array_merge($result_item, array($property => $property_value));
			}
		}
		$result = $tmp;
	}
	return $result;
}


$data = array(
    range('a', 'z'),
    range('a', 'z'),
    range('a', 'z'),
    range('a', 'z'),
    range('a', 'z'),
);


$combos = generate_combinations($data);
echo sizeof($combos);
echo "\n";
echo "not real: ".(memory_get_peak_usage(false)/1024/1024)." MiB\n";
echo "real: ".(memory_get_peak_usage(true)/1024/1024)." MiB\n\n";