I am building a templating engine and would like to allow nested logic.
I need to split the following string using "@" for the delimiter but would like to ignore this delimiter - treat is as just another character - if its inside the [square brackets].
Here is the input string:
@if(param1>=7) [ something here @if(param1>9)[ nested statement ] ] @elseif(param2==true) [ 2st condition true ] @else [ default condition ]
The result should look like:
array(
" if(param1>=7) [ something here @if(param1>9)[ nested statement ] ] ",
" elseif(param2==true) [ 2st condition true ] ",
" else [ default condition ] "
)
I believe preg_split is what Im looking for but could use help with the regex
Regex:
@(?> if | else (?>if)? ) \s* # Match a control structure
(?> \( [^()]*+ \) \s*)? # Match statements inside parentheses (if any)
\[ # Match start of block
(?:
[^][@]*+ # Any character except `[`, `]` and `@`
(?> \\.[^][@]* )* (@+ (?! (?> if | else (?>if)? ) ) )? # Match escaped or literal `@`s
| # Or
(?R) # Recurs whole pattern
)* # As much as possible
\]\K\s* # Match end of container block
PHP:
print_r(preg_split("~@(?>if|else(?>if)?)\s*(?>\([^()]*+\)\s*)?\[(?:[^][@]*+(?>\\.[^][@]*)*(@+(?!(?>if|else(?>if)?)))?|(?R))*\]\K\s*~", $str, -1, PREG_SPLIT_NO_EMPTY));
Output:
Array
(
[0] => @if(param1>=7) [ something here @if(param1>9)[ nested statement ] ]
[1] => @elseif(param2==true) [ 2st condition true ]
[2] => @else [ default condition ]
)
To match nested brackets, you need to use a recursive pattern.
(?:(\[(?:[^[\]]|(?1))*])|[^@[\]])+
It will match each segment, not including the leading @. It will also capture the last bracket into group 1, which you can ignore.
Use the pattern with preg_match or preg_match_all.
Thank you for you replies! Revo's answer worked!
I was unable to come up with the regex myself and have instead built a parser function that works as well. Perhaps it can be useful to somebody:
function parse_context($subject) { $arr = array(); // array to return
$n = 0; // number of nested sets of brackets
$j = 0; // current index in the array to return, for convenience
$n_subj = strlen($subject);
for($i=0; $i<$n_subj; $i++){
switch($subject[$i]) {
case '[':
$n++;
$arr[$j] .= '[';
break;
case ']':
$n--;
$arr[$j] .= ']';
break;
case '@':
if ($n == 0) {
$j++;
$arr[$j] = '';
break;
}
default: $arr[$j].=$subject[$i];
}
}
return $arr;
} // parse_context()