使用preg_replace（）替换特殊字符之间的内容

Question

I have a paragraph as -

== one ===

==== two ==

= three ====

etc.

The number of = sign vary in every row of the paragraph.

I want to write a preg_replace() expression that will allow me to replace the texts between the = signs.

example:

== DONE ===

==== DONE ==

= DONE ====

I tried preg_replace("/\=+(.*)\=+/","DONE", $paragraph) but that doesn't work. Where am I going wrong?

Answer 1

You can use:

$str = preg_replace('/^=+\h*\K.+?(?=\h*=)/m', 'DONE', $str);

RegEx Demo

RegEx Breakup:

^          # Line start
=+         # Match 1 or more =
\h*        # Match or more horizontal spaces 
\K         # resets the starting point of the reported match
.+?        # match 1 or more of any character (non-greedy)
(?=\h*=)   # Lookahead to make sure 0 or more space followed by 1 = is there