如何使用正则表达式将文本样式更改为特定样式？

Question

I have a textarea like what is in stackoverflow's ask-page. Now I want to replace some text to some specific pattern. In other word I want to add some tags around a text. I want something like these:

**bold**
__underline__
*italics*
--strike--
[linkname](www.example.com)

Well, I'm newbie to PHP... But I did it using javascript:

text.replace(/\*\*(.*?)\*\*/g, "<b>$1</b>");
text.replace(/__(.*?)__/g, "<u>$1</u>");
text.replace(/\*(.*?)\*/g, "<i>$1</i>");
text.replace(/--(.*?)--/g, "<del>$1</del>");

// also I didn't know do that for link-href
// I want this: <a href="www.example.com">linkname</a>

So, how can I do that using php? (I want to check the content both client-side and server-side, Because maybe javacript is deactivate on some of visitor's system)

Answer 1

For PHP there is a function called preg_replace , this is the one you are searching for.

For your second problem with the link, you could do something like this, this makes a simple check, to be sure that the URL is valid.
(?:^\\[)(.*?)(?:\\]\\()(www\\..+?\\.\\D+?)(?:\\))

UPDATE 1:
Simple use with my regex as requested:
<?php $string = '[linkname](www.example.com)'; $pattern = '/(?:^\\[)(.*?)(?:\\]\\()(www\\..+?\\.\\D+?)(?:\\))/'; $replacement = '${1}, $2'; echo preg_replace($pattern, $replacement, $string);

For doing all of this easier you can use this PHP class: (Suggested by @miken32):
https://github.com/erusev/parsedown/blob/master/Parsedown.php#L1171