Strip all BBCode from string, except for [quote]

Question

I want to be able to strip all BBCode from a string, except for the [quote] BBCode.

I have the following patterns that could be possible for quotes:

[quote="User"]
[quote=User]
[quote]
Text
[/quote]
[/quote]
[/quote]

This is what I currently use to strip the BBCode that works:

$pattern = '|[[\/\!]*?[^\[\]]*?]|si';
$replace = '';
$quote = preg_replace($pattern, $replace, $tag->content);

Answer 1

Pretty much some solutions

<?php
  function show($s) {
    static $i = 0;
    echo "<pre>************** Option $i ******************* \n" . $s . "</pre>";
    $i++;
  }

  $string = 'A [b]famous group[/b] once sang:
    [quote]Hey you,[/quote]
    [quote mlqksmkmd]No you don\'t have to go[/quote]

    See [url
    http://www.dailymotion.com/video/x9e7ez_pony-pony-run-run-hey-you-official_music]this video[/url] for more.';

  // Option 0
  show($string);

  // Option 1: This will strip all BBcode without ungreedy mode
  show(preg_replace('#\[[^]]*\]#', '', $string));

  // Option 2: This will strip all BBcode with ungreedy mode (Notice the #U at the end of the regex)
  show(preg_replace('#\[.*\]#U', '', $string));

  // Option 3: This will replace all BBcode except [quote] without Ungreedy mode
  show(preg_replace('#\[((?!quote)[^]])*\]#', '', $string));

  // Option 4: This will replace all BBcode except [quote] with Ungreedy mode
  show(preg_replace('#\[((?!quote).)*\]#U', '', $string));

  // Option 5: This will replace all BBcode except [quote] with Ungreedy mode and mutiple lines wrapping
  show(preg_replace('#\[((?!quote).)*\]#sU', '', $string));
?>

So actually, it's just a choice between option 3 and 5 I think.

• [^]] selects every char which isn't a ]. It allows to "emulate" ungreedy mode.
• U regex option allows us to use .* instead of [^]]*
• s regex option allows to match on multiple lines
• (?!quote) allows us to say anything that doesn't match "quote" in the next selection. It is used this way: ((?!quote).)*. See Regular expression to match a line that doesn't contain a word? for more info.

This fiddle is a live demo.