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  1. <?php
  2.  
  3. $data = <<<DATA
  4. Here is some normal post content
  5.  
  6. [QUOTE]
  7. This is an appropriate quote
  8. [/QUOTE]
  9.  
  10. Here is more post content
  11.  
  12. [QUOTE]
  13. This is a a valid quote, as it's only 1 level deep.
  14.    [QUOTE="User 2"]
  15.    Here's an unnecessary nested quote.
  16.        [QUOTE]
  17.        Here's a 3nd level unnecessary nested quote.
  18.        [/QUOTE]
  19.    [/QUOTE]
  20. [/QUOTE]
  21.  
  22. Here is more post content
  23. DATA;
  24.  
  25. $regex = '~
  26. 				(\[QUOTE[^][]*\]
  27. 				(?:[^][]++|(?1))++
  28. 				\[/QUOTE\])
  29. 				~x';
  30.  
  31. $data = preg_replace_callback($regex, 
  32. 	function($match) use($regex) {
  33. 		return $match[0][0] . preg_replace($regex, '', substr($match[0], 1));
  34. 	},
  35. 	$data);
  36. echo $data;
  37. ?>
Success #stdin #stdout 0.02s 23776KB
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Standard input is empty
stdout
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Here is some normal post content

[QUOTE]
This is an appropriate quote
[/QUOTE]

Here is more post content

[QUOTE]
This is a a valid quote, as it's only 1 level deep.
   
[/QUOTE]

Here is more post content
https://ideone.com/s7Zvpy
language:
PHP (php 7.3.5)
created:
7 years ago
visibility:
public

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