Regexp tip request - php

Question

I have a string like
"first,second[,b],third[a,b[1,2,3]],fourth[a[1,2]],sixth"
I want to explode it to array
Array (
0 => "first",
1 => "second[,b]",
2 => "third[a,b[1,2,3]]",
3 => "fourth[a[1,2]]",
4 => "sixth"
}
I tried to remove brackets:
preg_replace("/[ ( (?>[^[]]+) | (?R) )* ]/xis",
"",
"first,second[,b],third[a,b[1,2,3]],fourth[a[1,2]],sixth"
);
But got stuck one the next step

Answer 1

PHP's regex flavor supports recursive patterns, so something like this would work:
$text = "first,second[,b],third[a,b[1,2,3]],fourth[a[1,2]],sixth";
preg_match_all('/[^,\[\]]+(\[([^\[\]]|(?1))*])?/', $text, $matches);
print_r($matches[0]);
which will print:
Array
(
[0] => first
[1] => second[,b]
[2] => third[a,b[1,2,3]]
[3] => fourth[a[1,2]]
[4] => sixth
)
The key here is not to split, but match.
Whether you want to add such a cryptic regex to your code base, is up to you :)
EDIT
I just realized that my suggestion above will not match entries starting with [. To do that, do it like this:
$text = "first,second[,b],third[a,b[1,2,3]],fourth[a[1,2]],sixth,[s,[,e,[,v,],e,],n]";
preg_match_all("/
( # start match group 1
[^,\[\]] # any char other than a comma or square bracket
| # OR
\[ # an opening square bracket
( # start match group 2
[^\[\]] # any char other than a square bracket
| # OR
(?R) # recursively match the entire pattern
)* # end match group 2, and repeat it zero or more times
] # an closing square bracket
)+ # end match group 1, and repeat it once or more times
/x",
$text,
$matches
);
print_r($matches[0]);
which prints:
Array
(
[0] => first
[1] => second[,b]
[2] => third[a,b[1,2,3]]
[3] => fourth[a[1,2]]
[4] => sixth
[5] => [s,[,e,[,v,],e,],n]
)