How to clean duplicate BB tags

Question

[i][b][i][b](This is a paragraph with BBcode.)[/b][/i][/b][/i]

Some of my BB code has double tags, whats the best way to remove this?

I've tried a few things mostly regex, but I'm honestly a novice when it comes to regex.

Answer 1

This is absolutely horrible, but it works.

<?php

$bb = '[i][b][i][b](This is a paragraph with BBcode.)[/b][/i][/b][/i]';

// regex with start, paragraph, and end capture groups
$regex = '#(?<start>(\[[a-z]*\])*+)(?<paragraph>.*)(?<end>(\[\/[a-z]*\])*+)#U';

// put matches into $matches array
preg_match_all($regex, $bb, $matches);

// get the stuff we need
$start = $matches['start'][0];         // string(12) "[i][b][i][b]"
$paragraph = implode('', $matches['paragraph']);

// now we will grab each tag
$regex = '#\[(?<tag>[a-z])\]#';
preg_match_all($regex, $start, $matches);
$tags = array_unique($matches['tag']);

// and build up the new string
$newString = '';
foreach($tags as $tag) {
    $newString .= '[' . $tag . ']';
}

// create the end tags
$end = str_replace('[', '[/', $newString);

// put it all together
$newString .= $paragraph . $end;

echo $newString; // [i][b](This is a paragraph with BBcode.)[/i][/b]

Which gives you [i][b](This is a paragraph with BBcode.)[/i][/b]

Check it here https://3v4l.org/O8UHO