Custom BB Codes

[enouwee]

If anyone has the patience to explain me, please . For example, a thing I would like to know would be how to make the url tag. Because, in the url tag you can pass 2 arguments (link and the actual text) and I am confused at it.

Here's the basic matching code, so you can see, what it does:

<?php

$string = '[a url="test"]this[B]a test[/a]';

if (preg_match(',\[(a|img)\s+url="([^"]*)"\](.*?)\[/\1\],i', $string, $matches))
{
        print_r($matches);
}

?>

There are tons of ways to proceed from here. I'd add PREG_OFFSET_CAPTURE to the flags passed to preg_match() and replace the BBCode, including URL and body after a thorough validation using substr_replace().

 

[monoVertex]

You know, you got me even deeper in the fog xD.

 

[enouwee]

You know, you got me even deeper in the fog xD.

No problem, I bet everything will be much clearer, once you see this. It's very easy, didn't even take 30 minutes to write:

<?php

$string = 'XX[a url="test"]this[B]a test[/a]YY';
$string .= 'ZZ[img url="my_test"]this an image test[/img]TT';

if (preg_match_all(',\[([a-z]+)\s+url="([^"]*)"\](.*?)\[/\1\],i', $string, $matches, PREG_OFFSET_CAPTURE))
{
        for ($i = count($matches[0]) - 1; $i >= 0; $i--)
        {
                $valid = true;

                $len = strlen($matches[0][$i][0]);
                $pos = $matches[0][$i][1];

                $tag = strtolower($matches[1][$i][0]);
                switch ($tag)
                {
                        case 'a':
                        case 'img':
                                // filter your other valid tags here
                                break;
                        default:
                                $valid = false;
                }

                if ($valid == true)
                {
                        // process URL part
                        $url = $matches[2][$i][0];

                        if (empty($url))
                        {
                                $valid = false;
                        }

                        // do other validation here
                }

                if ($valid == true)
                {
                        // process body part
                        $body = $matches[3][$i][0];

                        if (empty($body))
                        {
                                $valid = false;
                        }

                        // do other validation here
                }

                if ($valid)
                {
                        switch ($tag)
                        {
                                case 'img':
                                        $output = '<img src="' . $url . '" alt="' . $body . '" />';
                                        break;
                                case 'a':
                                        $output = '<a href="' . $url . '">' . $body . '</a>';
                                        break;
                        }
                }
                else
                {
                        $output = '';
                }

                $string = substr_replace($string, $output, $pos, $len);

                print "ITERATION USING MATCH $i:\n";
                print "$string\n\n";
        }

        print "FINAL RESULT:\n$string\n";
}


?>

 

[monoVertex]

Meh, I started to understand these functions better. I made myself a piece of code which is supposed to replace the url tags.

$text = preg_replace('/(\[url=) (.*?) (\]) (.*?) (\[\/url\])/i','<a href="$2">$4</a>',$text);

I see no syntax problem, and it's supposed to work... However, the url tags are still displayed as literal on the page...

 

[enouwee]

$text = preg_replace('/(\[url=) (.*?) (\]) (.*?) (\[\/url\])/i','<a href="$2">$4</a>',$text);

I see no syntax problem, and it's supposed to work... However, the url tags are still displayed as literal on the page...

What are you trying to do? I see a lot of useless spaces in that expression.

If you want to replace something like this:
[url.=THIS_IS_MY_URL]THIS IS MY TEXT[/url.] (ignore . due to parsing problem)

better use an expression like:

$text = preg_replace(',\[url=\s*(.*?)\s*\]\s*(.*?)\s*\[/url\],i','<a href="$1">$2</a>',$text);

Note that some captures are useless, as you don't use them and \s* matches any number of whitespaces, including 0.

 

[monoVertex]

Thank you! One more question . If there are line breaks inside the tags, they are not parsed. How cam I make the function to ignore line breaks?

 

[enouwee]

Thank you! One more question . If there are line breaks inside the tags, they are not parsed. How cam I make the function to ignore line breaks?

If you want the "." to match newlines, you have to add a "s" modifier, like:

/line1.*line2/s

Alternatively, the "m" modifier changes the behaviour of "^" to match every "begin of line" and not only the "begin of the string".

The full list of supported modifiers is:
http://www.php.net/manual/en/reference.pcre.pattern.modifiers.php

 

[monoVertex]

Hmmm... It's not supposed to match new lines, I can have something like this:

[font.=verdana]test


test
test
test

test
[/verdana]

This is not parsed and the first "test" is not on a new line.

EDIT: Nvm, studied that list and understood, it's all working now, thanks a lot!

 

[enouwee]

EDIT: Nvm, studied that list and understood, it's all working now, thanks a lot!

This works like a charm:

<?php

$string ='[font=verdana]test


test
test
test

test
[/font]';

print_r(preg_replace('!\[font=(.*?)\](.*?)\[/font\]!is', '<font face="$1">$2</font>', $string));

?>

 

[monoVertex]

Yeah, I saw that . Gotta spread first . You are credited on the page, anyway .

 

[enouwee]

Yeah, I saw that . Gotta spread first . You are credited on the page, anyway .

If you want to implement your BBCode like that, please don't put my name next to it. phyrex1an already said it the previous posts, I'm going to repeat it:
Don't blindly use that preg_replace() thing without any additional validation steps, as your code will be vulnerable to XSS (cross-site scripting) attacks.

You have to filter both inputs, either by limiting the choices or filtering out malicious content. Rather than saying "(.*?)", you'd use "(arial|times|courier)" to set the font family from a given subset. preg_replace_callback() allows you to do post-processing on the matches: a callback function generates the replacement string.

I put a much larger piece of code in #23, which takes the whole input apart and later replaces it (without preg_replace_callback(), but essentially, both do the same). You can transform and validate the fields as you like before they're inserted back into the text.