Splitting string into sections while maintaining all non-word characters - php

Question

I'm working on an encryption function just for fun (for a non-production environment). Currently running my encrypt function like this:
encrypt("This is a string.");
Produces the following string:
GnulHynkAfdsGknp AfdsGknp Wgbf GknpLnugBuipAfdsCbhgByfg.
This is perfect, exactly what I wanted and expected - however, now I'm trying to write a decrypt function. Every character that is encrypted will have a single capital letter followed by 3 non-capital letters (As you can see from the example above).
My plan was to run preg_split() to get the different letters of the string.
Here is my current PHP code (pattern ([A-Z][a-z]{3})):
print_r(preg_split("/([A-Z][a-z]{3})/", $string));
There are a couple of problems with this. While testing, I discovered that it is not returning what I expected, the return is:
Array
(
[0] =>
[1] =>
[2] =>
[3] =>
[4] =>
[5] =>
[6] =>
[7] =>
[8] =>
[9] =>
[10] =>
[11] =>
[12] =>
[13] => .
)
(Via eval.in)
So this has the proper amount of returns, but they are all blank. Why are all the values blank?
Another thing that I thought of was that I needed to include other characters such as spaces, commas, periods etc in the preg_split() return. In the return I got from eval.in, it appears as though the final period has been included. Is this true for spaces and other characters as well, or do I need to do something special in cases of these characters?

Answer 1

It's "splitting" on those matches so they are removed. You want preg_match_all or use PREG_SPLIT_DELIM_CAPTURE with PREG_SPLIT_NO_EMPTY.
print_r(preg_split("/([A-Z][a-z]{3})/",
$string,
null,
PREG_SPLIT_DELIM_CAPTURE|PREG_SPLIT_NO_EMPTY));

Answer 2

You should remove capturing group () and use preg_match_all.
$text = "GnulHynkAfdsGknp AfdsGknp Wgbf GknpLnugBuipAfdsCbhgByfg.";
preg_match_all("/[A-Z][a-z]{3}|(?: |,|\.)/", $text, $match);
print_r($match);
Output:
Array
(
[0] => Array
(
[0] => Gnul
[1] => Hynk
[2] => Afds
[3] => Gknp
[4] =>
[5] => Afds
[6] => Gknp
[7] =>
[8] => Wgbf
[9] =>
[10] => Gknp
[11] => Lnug
[12] => Buip
[13] => Afds
[14] => Cbhg
[15] => Byfg
[16] => .
)
)