Question

The below matches when there’s excess white space. Now I need it to match regardless of what’s in between it… I tried replacing \s* with .+? but that didn’t work. I’m looking at a regex cheat sheet and can’t figure out the most efficient way to do this.

preg_replace("/<sup>(\s*)$key(\s*)<\/sup>/i", "<sup>$val</sup>", $text);

Should match: <sup>(anything here){$key}(anything here)</sup>

update

This is sad… I just realized the regex I’m working with doesn’t need to match whitespaces, but a <br> tag… something like

$text = preg_replace("/<sup>([\s\n(<br>)]*)$key([\s\n(<br>)]*)<\/sup>/is", "<sup>$val</sup>", $text);

Answer 1

I’m not entirely sure I understand, but if you want .*? to also match newlines, you need the /s modifier:

preg_replace("#<sup>(.*?)$key(.*?)</sup>#is", "<sup>$val</sup>", $text);

Be aware though, that this might match more than you think. If you have more than one <sup> tag, and only the last one contains $key, the regex will match all the way from the first <sup> to the last </sup>! So better be specific about what you want to allow there.

I’d suggest you use (?:(?!</?sup).)* instead of .*? in the above regex. This ensures that you’ll never match across tag boundaries:

(?:       # Try to match...
 (?!      #  (as long as it's impossible to match
  </?sup #   <sup or </sup
 )        #   at the current position)
 .        # ... any character.
)*        # Do this any number of times.

So, in the end, you get:

preg_replace("#<sup>(?:(?!</?sup).)*$key(?:(?!</?sup).)*</sup>#is", "<sup>$val</sup>", $text);