<?php
$input_lines="any word here related to #English must #be replaced.";
$output = preg_replace("/(#\w+)/", "<a href='bla bla'>$1</a>", $input_lines);
echo $output;
any word here related to <a href='bla bla'>#English</a> must <a href='bla bla'>#be</a> replaced.
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0
any word here related to <a href='bla bla'>#English</a> must <a href='bla bla'>#be</a> replaced.