Question

I can’t work out how to get my Regex to select multiple lines, when I’m using

[b]Test[/b]

my BB code works fine but when I try

[b]
Test
[/b]

I have read that I should use the modifiers /s /m in my regex but I don’t know how to, I have tried: preg_match_all(‘\[(' . $tags . ')=?(.*?)\](.+?)\[/\1\]/m/s‘ but it doesnt work.

Any Suggestions?

Working example:

$tags = 'b|i|size|color|center|quote|url|img';
while (preg_match_all('`\[(' . $tags . ')=?(.*?)\](.+?)\[/\1\]`', $string, $matches))
    foreach ($matches[0] as $key => $match) {
        list($tag, $param, $innertext) = array($matches[1][$key], $matches[2][$key], $matches[3][$key]);

Answer 1

Your syntax for adding modifiers is not right. Firstly, you do not need any slashes to apply them. They just belong after the delimiter (which in your case is not / but `). And also you do not need to delimit every single modifier again, just stick them together:

'`\[(' . $tags . ')=?(.*?)\](.+?)\[/\1\]`ms'

Which delimiter you use does not matter at all. Check out PHP documentation on delimiters. You can use

any non-alphanumeric, non-backslash, non-whitespace character.

Just be careful that the delimiter has to be escaped. So there is no difference between ` and / at all. Just if you use / instead, then you need to escape / within the regex (otherwise PHP will assume that this is the end of the regex). Like this:

'/\[(' . $tags . ')=?(.*?)\](.+?)\[\/\1\]/ms'

Therefore, the choice of delimiter is mostly a matter of convenience – use one that does not occur within the regex if possible, so you do not have to escape it. / is simply the most common choice, which is why you have probably found the /m notation for adding modifiers. As the PHP documentation states are common choices are # and ~ (I have also seen ! quite often).