Parse string with regex and get desired output - php

Question

I want to parse this string
[[delay-4]]Welcome! [[delay-2]]Do you have some questions for us?[[delay-1]] Please fill input field!
I need to get something like this:
[
[0] => '[[delay-4]]Welcome!',
[1] => '[[delay-2]]Do you have some questions for us?',
[2] => '[[delay-1]] Please fill input field!
];
String can also be something like this (without [[delay-4]] on beginning):
Welcome! [[delay-2]]Do you have some questions for us?[[delay-1]] Please fill input field!
Expected output should be something like this:
[
[0] => 'Welcome!',
[1] => '[[delay-2]]Do you have some questions for us?',
[2] => '[[delay-1]] Please fill input field!
];
I tried with this regex (https://regex101.com/r/Eqztl1/1/)
(?:\[\[delay-\d+]])?([\w \\,?!.##$%^&*()|`\]~\-='\"{}]+)
But I have problem with that regex if someone writes just one [ in text, regex fails and if I include [ to match I got wrong results.
Can anyone help me with this?

Answer 1

Two simpler actions might be the route to get the result:
$result = preg_replace('/\s*(\[\[delay-\d+]])/i', "\n$1", $subject);
$result = preg_split('/\r?\n/i', $result, -1, PREG_SPLIT_NO_EMPTY);
Can be seen running here:
https://ideone.com/Z5tZI3
and here:
https://ideone.com/vnSNYI
This assumes that newline characters don't have special meaning and are OK to split on.
UPDATE: As noted in the comments below it's possible with a single split.
$result = preg_split('/(?=\[\[delay-\d+]])/i', $subject, -1, PREG_SPLIT_NO_EMPTY);
But there are possible issues with zero-length matches and regular expressions, you would have to do your own research on that.

Answer 2

In your pattern (?:[[delay-\d+]])?([\w \,?!.##$%^&*()|`]~-='\"{}]+)
there is no opening [ in the character class. The problem is that if you add it, you get as you say wrong results.
That is because after matching after matching delay, the character class in the next part which now contains the [ can match the rest of the characters including those of the delay part.
What you could do is to add [ and make the match non greedy in combination with a positive lookahead to assert either the next match for the delay part or the end of the string to also match the last instance.
If you are not using the capturing group and only want the result you can omit it.
(?:\[\[delay-\d+]])?[\w \\,?!.##$%^&*()|`[\]~\-='\"{}]+?(?=\[\[delay-\d+]]|$)
Regex demo | Php demo

Answer 3

You can do that without regex too.
Explode on [[ and loop the array. If the start of the item is "delay" then add [[
$str = '[[delay-4]]Welcome! [[delay-2]]Do you have some questions for us?[[delay-1]] Please fill input field!';
$arr = array_filter(explode("[[", $str));
foreach($arr as &$val){
if(substr($val,0,5) == "delay") $val = "[[" . $val;
}
var_dump($arr);
https://3v4l.org/sIui1