Question

I’ve not yet mastered regex, so would appreciate your help with the code.

I need to replace all lines that:

1. start with brackets or parentheses;
2. which may contain either a regular number of up to 3 digits or a combination of up to 3 letters;
3. which may be followed by a period;
4. 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] &nbsp;some stuff => %%[b]|&nbsp;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

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;
        }
    }
}
$strings = array(
    '(1)blahblah',
    '(<i>iv</i>.) blahblah',
    '[b] &nbsp;some stuff',
    '25. blahblah',
    'A. some other stuff. one',
    'blah. some other stuff',
    'text (1) text',
    '2008. blah',
    '[123) <-- mismatch'
);
foreach($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';