How to add a condition to the regular expression "Is there any characters before the match"?

Question

PHP

You need to make a regular expression that replaces hashtags with links.
Here is the code that does it:

$pattern = "/\#(\w+)/ui";
$text = preg_replace($pattern, '<a href="'.site_url().'?s=%23$1&bp_search=1&view=content" target="_blank">#$1</a>',$text);

The problem is that, for example, if you add an emoji, it will have the code "& # x1f601 (No spaces, the editor does not skip)" and the regular expression replaces this line.
How to make a condition to check if there is something before the # sign (Except for a space) and if there is , then do not add a link.

Answer 1

Here is /(?<![&])(?:\B)#(\w+)/iu
https://regex101.com/r/0tnI4B/1 (the g flag was set for clarity)
Ps if necessary, it will /(?<![&])#(\w+)/iucapture the "text#tag" https://regex101.com/r/1PUO2t/1 (the g flag was set for clarity )