Removing everything except numbers inside braces and some characters

Question

Want to remove everything except # NewLine, complete bracket set and numbers inside braces.
Sample input:

# (1296) {20} [529] [1496] [411]
# (MONDAY ) (1296)
# (646) {20} (BEACH 7) [20 Mtrs] { 03 Foot }
# {19} [455] [721] (1296) (SUNDAY ) [2741] (MONDAY (WEDNESDAY {20}
# {19} (1296)

Code which does not work:

$re = '/(?:\[[^][]*]|\([^()]*\)|{[^{}]*})(*SKIP)(*F)|[^][(){}@#]+/m';
$result = preg_replace($re, '', $input);

Incorrect output:

#(1296){20}[529][1496][411]
#(1296) 
#(646){20}(BEACH 7)[20 Mtrs]{ 03 Foot }
#{19}[455][721](1296)[2741](({20}
#{19}(1296)

Desired output:

#(1296) {20} [529] [1496] [411]
#(1296)
#(646) {20}
#{19} [455] [721] (1296) [2741] {20}
#{19} (1296)

Answer 1

You could match at least 1 digit between the brackets and then skip that match.

Then match any char except a newline or # to be replaced with an empty string.

(?:\[\h*\d[\h\d]*]|\(\h*\d[\h\d]*\)|{\h*\d[\h\d]*})\h*(*SKIP)(*F)|[^#\n]

Explanation

• (?: Non capture group
  • \[\h*\d[\h\d]*] Match at least 1 digit between square brackets, where \h matches horizontal whitespace characters (no newlines)
  • | Or
  • \(\h*\d[\h\d]*\) 1 digit between parenthesis
  • | Or
  • {\h*\d[\h\d]*} 1 digit between curly braces
• )\h* Close the non capture group and match 1+ spaces
• (*SKIP)(*F) Skip and fail the match (to leave it untouched in the output)
• | Or
• [^#\n] Match any character except # or a newline

Regex demo