Remove spaces before and after parentheses

Question

I'm trying to remove one or more spaces after open parentheses and before close parentheses for both round and square parentheses.

$s = "This is ( a sample ) [ string ] to play with"

expected result:

"This is (a sample) [string] to play with"

I managed to remove the space before:

$s = preg_replace('/\s+(?=[\])])/', '', $s);

result:

"This is ( a sample) [ string] to play with"

but not the spaces after the parentheses!

Answer 1

Try this regex:

(?<=[([]) +| +(?=[)\]])

Click for Demo

Replace the matches with a blank string

Explanation:

• (?<=[([]) + - matches 1+ occurrences of a space which are preceded by either a [ or (
• | - OR
• +(?=[)\]]) - matches 1+ occurrences of a space which are followed either by ) or ]