Please help me write regex replace - php

Question

I've not yet mastered regex, so would appreciate your help with the code.
I need to replace all lines that:
start with brackets or parentheses;
which may contain either a regular number of up to 3 digits or a combination of up to 3 letters;
which may be followed by a period;
which digis or the numbers may or may not be inside or tags.
Here's the example of what it needs to be replaced with:
(1)blahblah => %%(1)|blahblah
(<i>iv</i>.) blahblah => %%(<i>iv</i>.)|blahblah
[b] some stuff => %%[b]| some stuff
So the regex will need to recognize if it needs to be applied to the particular string, and if yes, put %% in the beginning of the line, then put the stuff inside the brackets, then put a pipe | (if there is a space between the brackets and the rest of the text, delete the space), and finally place the rest of the line.
So, let's assume I have an array that I'm trying to run through the function that will either process the string (if it matches the criteria), or return it unchanged.
I only need to know how to write the function.
Thanks

Answer 1

function my_replace ($str) {
$expr = '~
(
# opening bracket or paren
(?:\(|\[)
# optional opening tag
(?:<([a-z])>)?
# either up to 3 digits or up to 3 alphas
(?:[a-z]{1,3}|[0-9]{1,3})
# optional closing tag
(?:</\2>)?
# optional dot
\.?
# closing bracket or paren
(?:\)|])
)
# optional whitespace
\s*
# grab the rest of the string
(.+)
~ix';
return preg_replace($expr, '%%$1|$3', $str);
}
See it working

Answer 2

Here is my version.
It uses the fallback regular expression if the first one doesn't match (as agreed upon previously).
Demo
Code:
<?php
function do_replace($string) {
$regex = '/^(\((?:<([a-z])>)?(\d{0,3}|[a-z]{1,3})(?:<\/\2>)?(\.)?\)|\[(?:<([a-z])>)?(\d{0,3}|[a-z]{1,3})(?:<\/\2>)?(\.)?\])\s*(.*)/i';
$result = preg_match($regex, $string);
if($result) {
return preg_replace($regex, '%%$1|$8', $string);
} else {
$regex = '/^(\d{0,3}|[a-z]{1,3})\.\s*(.+)$/i';
$result = preg_match($regex, $string);
if($result) {
return preg_replace($regex, '%%$1.|$2', $string);
} else {
return $string;
}
}
}
$strings = array(
'(1)blahblah',
'(<i>iv</i>.) blahblah',
'[b] some stuff',
'25. blahblah',
'A. some other stuff. one',
'blah. some other stuff',
'text (1) text',
'2008. blah',
'[123) <-- mismatch'
);
foreach($strings as $string) echo do_replace($string) . PHP_EOL;
?>
First regular expression expanded:
$regex = '
/
^(
\(
(?:<([a-z])>)?
(
\d{0,3}
|
[a-z]{1,3}
)
(?:<\/\2>)?
(\.)?
\)
|
\[
(?:<([a-z])>)?
(
\d{0,3}
|
[a-z]{1,3}
)
(?:<\/\2>)?
(\.)?
\]
)
\s*
(.*)
/ix';

Answer 3

function replaceString($string){
return preg_replace('/^\s*([\{,\[,\(]+?)/', "%%$1", $string);
}