如何从php的字符串中解析出特定的“标签”

Question

I like how StackOverflow allows you to search for tags by specifying [tagname] in the search field. How could I go about writing a parser that would help me separate out tags from normal text. I can think of the manual way which would be to use some combination of substring and/or regex to get the position of opening and closing square brackets, and then extract out those strings, but I'm curious if there's a better way (and my regex skill is subpar at best)

// example
$query = 'How to use [jQuery] [selector] selectors';
$tags = getTags($query); // $tags == 'jQuery, selector'
$text = getText($query); // $text == 'How to use selectors'

Answer 1

Regex would probably work best, just don't try to parse HTML. https://www.debuggex.com/ Is a really good site for visually seeing what your regex string is doing. I would recommend reading up on the PHP regex functions, and learn some more, there is a cheatsheat at the bottom of the site.

.*[(tag)].*

Would work to get the tags, using a captured group. The preg_match_all function is really good for working with multiple results, just make sure to read the official documentation to get it working how you need it.

For parsing more complex, or irregular things (like html, which is extremely difficult to do reliably), it is better to do it manually. Regex has worked for all my non HTML parsing needs in the past.

Answer 2

Regular Expressions are probably the way to go. The more you can specify about how the tags are set the easier it will be to capture the right ones (In the expression below I limit it to either letters \\w or numbers \\d . The function uses a capture group (enclosed in parens) to pull out the relevant tags.

function getTags($query) {
    preg_match_all("/\[([\w\d]+)\]/", $query, $matches);
    return $matches;
}