PHP: RegEx for nested {IF} {ENDIF} Conditions

Question

I am searching the whole day for a RegEx that matches just the inner {IF} - {ENDIF}-Statement in a nested condition code. Does anyone have an idea?

for example:

{IF bla}Text 1{ELSEIF ble}Text 2 {IF bli}Text 2.1{ELSE blo}Text 2.1{ENDIF} Main text end{/ENDIF}

I just want to get

{IF bli}Text 2.1{ELSE blo}Text 2.1{ENDIF}

i tried #\{IF .*\}.*\{ENDIF\}#is but this is not working as i only get the whole string.

And also important: The code can have several lines and line breaks!

the bla, ble, bli etc are dynamic and can differ

I dont think regexp is the way here (similiar to parsing XML/HTML). I would consider parsing text manualy (traversing text, when you hit { you check for keyword). This way you can build a tree yourself and then take any node you need. — insider
– insider, Commented Aug 27, 2017 at 22:19
thanks, after long searching and failing i used that solution. — user7213923
– user7213923, Commented Aug 29, 2017 at 11:00

linden2015 · Accepted Answer · 2017-08-27 22:49:44Z

1

Inner IF-ELSE:

{IF(?!.*{IF).*?}.*?{ENDIF}

(?!.*{IF) looks ahead from that position and asserts it won't match
The lazy quantifiers ? are an instruction to stop at the earliest match.

Demo

answered Aug 27, 2017 at 22:49

linden2015

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Comments

mickmackusa · Accepted Answer · 2017-08-27 23:14:53Z

0

This grabs your inner IF block:

/{IF(?:.*?(?={IF)(*SKIP)(*FAIL)|.*?){ENDIF}/

Demo (279 steps)

The pattern uses (*SKIP)(*FAIL) and "disqualifies" any IF blocks that contain an inner IF block. This way you only get the innermost IF block.

Code: (Demo)

$string='{IF bla}Text 1{ELSEIF ble}Text 2 {IF bli}Text 2.1{ELSE blo}Text 2.1{ENDIF} Main text end{/ENDIF}';
echo  preg_match('/{IF(?:.*?(?={IF)(*SKIP)(*FAIL)|.*?){ENDIF}/',$string,$match)?$match[0]:'fail';

Output:

{IF bli}Text 2.1{ELSE blo}Text 2.1{ENDIF}

Or faster/better with negative lookahead:

/{IF(?!.*{IF).*?{ENDIF}/

Demo (190 steps)

edited Aug 27, 2017 at 23:14

answered Aug 27, 2017 at 22:25

mickmackusa♦

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