PHP string expansion - php

Question

I have a string composed by many letters, at some point, one letter from a group can be used and this is represented by letters enclosed in []. I need to expand these letters into its actual strings.
From this:
$str = 'ABCCDF[GH]IJJ[KLM]'
To this:
$sub[0] = 'ABCCDFGIJJK';
$sub[1] = 'ABCCDFHIJJK';
$sub[2] = 'ABCCDFGIJJL';
$sub[3] = 'ABCCDFHIJJL';
$sub[4] = 'ABCCDFGIJJM';
$sub[5] = 'ABCCDFHIJJM';
UPDATE:
Thanks to #Barmar for the very valuable suggestions.
My final solution is:
$str = '[GH]DF[IK]TF[ADF]';
function parseString(string $str) : array
{
$i = 0;
$is_group = false;
$sub = array();
$chars = preg_split('//', $str, -1, PREG_SPLIT_NO_EMPTY);
foreach ($chars as $key => $value)
{
if(ctype_alpha($value))
{
if($is_group){
$sub[$i][] = $value;
} else {
if(!isset($sub[$i][0])){
$sub[$i][0] = $value;
} else {
$sub[$i][0] .= $value;
}
}
} else {
$is_group = !$is_group;
++$i;
}
}
return $sub;
}
The recommended function for combinations is (check the related post):
function array_cartesian_product($arrays)
{
$result = array();
$arrays = array_values($arrays);
$sizeIn = sizeof($arrays);
$size = $sizeIn > 0 ? 1 : 0;
foreach ($arrays as $array)
$size = $size * sizeof($array);
for ($i = 0; $i < $size; $i++) {
$result[$i] = array();
for ($j = 0; $j < $sizeIn; $j++)
array_push($result[$i], current($arrays[$j]));
for ($j = ($sizeIn - 1); $j >= 0; $j--) {
if (next($arrays[$j]))
break;
elseif (isset($arrays[$j]))
reset($arrays[$j]);
}
}
return $result;
}
Check the solution with:
$combinations = array_cartesian_product(parseString($str));
$sub = array_map('implode', $combinations);
var_dump($sub);

Answer 1

Convert your string into a 2-dimensional array. The parts outside brackets become single-element arrays, while each bracketed trings becomes an array of single characters. So your string would become:
$array =
array(array('ABCCDF'),
array('G', 'H', 'I'),
array('IJJ'),
array('K', 'L', 'M'));
Then you just need to compute all the combinations of those arrays; use one of the answers at How to generate in PHP all combinations of items in multiple arrays. Finally, you concatenate each of the resulting arrays with implode to get an array of strings.
$combinations = combinations($array);
$sub = array_map('implode', $combinations);