regex bbcode and hyperlink from string

Question

[url=http://stackoverflow.com]stackoverflow[/url]
[url=http://stackoverflow.com]http://stackoverflow.com[/url]
http://stackoverflow.com
[url=http://stackoverflow.com][img]url_to_img[/img][/url]
[url=http://stackoverflow.com][b]stackoverflow[/b][/url]
[url=http://stackoverflow.com][b][u][i]stackoverflow[/i][/u][/b][/url]
[url=http://stackoverflow.com][color=red]stackoverflow[/color][/url]
[url=http://stackoverflow.com][h1][color=red]stackoverflow[/color][/h1][/url]

Change it to this:

<a href="http://stackoverflow.com">stackoverflow</a>
<a href="http://stackoverflow.com">http://stackoverflow.com</a>
<a href="http://stackoverflow.com">http://stackoverflow.com</a>
<a href="http://stackoverflow.com"><img src="url_to_img" /></a>
<a href="http://stackoverflow.com"><strong>stackoverflow</strong></a>
<a href="http://stackoverflow.com"><span style="color:red">stackoverflow</span></a>
<a href="http://stackoverflow.com"><h1><span style="color:red">stackoverflow</span></h1></a>

I tried find something what replace all not bbcode url.
I tried used https://github.com/wookieb/bbcode but when I upgrade php 5.2 to 5.5 stop working.
I tried used http://jbbcode.com/ but not parse url from string.

Morten · Accepted Answer · 2015-08-25 21:36:22Z

1

I have rebuild all but one line, the one with only the url.

<?php
$input = "[url=http://stackoverflow.com]stackoverflow[/url]
[url=http://stackoverflow.com]http://stackoverflow.com/damn[/url]
http://stackoverflow.com/ok
[url=http://stackoverflow.com][img]url_to_img[/img][/url]
[url=http://stackoverflow.com][b]stackoverflow[/b][/url]
[url=http://stackoverflow.com][b][u][i]stackoverflow[/i][/u][/b][/url]
[url=http://stackoverflow.com][color=red]stackoverflow[/color][/url]
[url=http://stackoverflow.com][h1][color=red]stackoverflow[/color][/h1][/url]";

$match = [
    '/\[url=([^\]]+)\](.*)\[\/url\]/im',
    '/\[img\](.*)\[\/img\]/im',
    '/\[b\](.*)\[\/b\]/im',
    '/\[u\](.*)\[\/u\]/im',
    '/\[i\](.*)\[\/i\]/im',
    '/\[color=([^\]]+)\](.*)\[\/color\]/im',
    '/\[h([1-6])\](.*)\[\/h(?:[1-6])\]/im',
];
$replace = [
    '<a href="$1">$2</a>',
    '<img src="$1">',
    '<strong>$1</strong>',
    '<u>$1</u>',
    '<em>$1</em>',
    '<span style="color:$1;">$2</span>',
    '<h$1>$2</h$1>',
];

echo preg_replace($match, $replace, $input);

This is giving the following output:

<a href="http://stackoverflow.com">stackoverflow</a>
<a href="http://stackoverflow.com">http://stackoverflow.com/damn</a>
http://stackoverflow.com/ok
<a href="http://stackoverflow.com"><img src="url_to_img"></a>
<a href="http://stackoverflow.com"><strong>stackoverflow</strong></a>
<a href="http://stackoverflow.com"><strong><u><em>stackoverflow</em></u></strong></a>
<a href="http://stackoverflow.com"><span style="color:red;">stackoverflow</span></a>
<a href="http://stackoverflow.com"><h1><span style="color:red;">stackoverflow</span></h1></a>

The one matching only the url is a bit trickier. It depends on how advanced you want it to be. It may detect simple stuff like example.com or more advanced stuff like ☃.net (which results in http://xn--n3h.net/)

Some explanation
First rule we are trying to match and replace is a url code. We simple start of by searching for appearance of [url=, simple and hardcoded. What we are looking for next might be a lot of things, but one thing we know for sure is that we have to end with a ]. We can then use a regular expression which says: match all but ] ([^\]]+) Note that I escaped the ] character, else the match will fail.
Next i again search for everything ((.*)) until we reach a hardcoded expected value, [/url].
This is pretty much the whole match rule for every type of bbcode you wanted.

As for the replace part you include what they should be replaced with, simple. To add the values matched in the regex, use $1, $2, ..., $n. A match is defined by my parentheses.
For an example: '/[url=([^]]+)](.*)[/url]/im'
The two parentheses segments in bold is the segments which contains the values we will be getting from $1and $2

I tried my best to explain how this worked. If something is still unclear, point it out, and I will try my best to explain further

edited Aug 25, 2015 at 21:36

answered Aug 25, 2015 at 21:09

Morten

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6 Comments

Robert Over a year ago

I've upvoted but you should give some explanation of your code to OP

Morten Over a year ago

Thanks for the upvote. Added some explanation at the bottom, or at least I tried to explain some parts as good as I could. If you got some suggestions to what more to explain or how to explain it different please let me know. @Robert

Robert Over a year ago

For sure you should not use greedy operators change .* to .*? if you know why then put two same bbcodes in your text and see what happen :)

Morten Over a year ago

Have been in this kind of situation before. A friend was working with a custom made forum and wanted a [quote] tag. Problem with .*? is that it takes its first ending while .* takes its last ending. I do however don't remember what I did with multiple inside at the top of my head, but I do think i used a recursive function to loop through and replace them all. @Robert

Pionas Over a year ago

Thaks work, fine. But what happend when i add somethink like that: [url=http://stackoverflow.com][b][u][i]stackoverflow[/i][/b][/u][/url] change to: <a href="http://stackoverflow.com">stackoverflow</a> or [url=http://stackoverflow.com][b][u][i]stackoverflow[/i][/u][/url] change to: <a href="http://stackoverflow.com">[b]stackoverflow</a> or what happend for this example: first paragraph... [h1]some title secong paragraph [h1]some title[/h1]

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