Simplify and Abstract my Code: Combining Strings - php

Question

I want to combine strings in PHP. My script creates every possible combination like below.
$part1 = array('','d','n','s','g');
$part2 = array('a','e','o','oo');
$part3 = array('m','n','s','d','l','t','g','j','p');
$part4 = array('g','p','l','');
$part5 = array('g','p','l');
$part6 = array('a','e','o');
$part7 = array('d','l','r','');
$names = array();
foreach ($part1 as $letter1) {
foreach ($part2 as $letter2) {
foreach ($part3 as $letter3) {
foreach ($part4 as $letter4) {
foreach ($part5 as $letter5) {
foreach ($part6 as $letter6) {
foreach ($part7 as $letter7) {
$names[] = $letter1 . $letter2 . $letter3 . $letter4 . $letter5 . $letter6 . $letter7;
}
}
}
}
}
}
}
But I am not happy with my solution. I is quick and dirty code. Is there a solution wich works with a flexible number of part arrays, so I can extend the script by e.g. $part8 easiely? (without changing the loop construction)

Answer 1

Recursive one:
function buildNames( $parts, $chars = ''){
// Nothing to do, shouldn't happen
if( !count( $parts)){
return array();
}
$names = array();
$part = array_shift( $parts);
// Max level, we can build final names from characters
if( !count( $parts)){
foreach( $part as $char){
$names[] = $chars . $char;
}
return $names;
}
// "We need to go deeper" and build one more level with remembered chars so far
foreach( $part as $char){
$names = array_merge( $names, buildNames( $parts, $chars . $char));
}
return $names;
}
$parts = array( $part1, $part2, $part3, $part4, $part5, $part6, $part7);
$names = buildNames( $parts);
From head, from scratch, comment if something, but idea should be good

Answer 2

You could reduce this problem to six cartesian products:
cartesianProduct($part1,
cartesianProduct($part2,
cartesianProduct($part3,
cartesianProduct($part4,
cartesianProduct($part5,
cartesianProduct($part6, $part7))))));
function cartesianProduct($p1, $p2) {
$ret = array();
foreach($p1 as $l1)
foreach($p2 as $l2)
$ret[] = $l1 . $l2;
return $ret;
}