[FIXED] How to replace text with a regex pattern and integrate a counter in the replacement text?

Issue

function parse($string){
    $counter = 0;
    
    $string = preg_replace("_\[b\](.*?)\[/b\]_si", '<span class="b">'. $counter .'. $1</span>', $string, -1, $counter);
    
    return $string;
}

I'm trying to make a ubb parser, that parses tags and put the counting in front of it:

[b]Hey[/b]
[b]Hello[/b]

Should return this:

<span class="b">1. Hey</span>
<span class="b">2. Hello</span>

But is returning this:

<span class="b">1. Hey</span>
<span class="b">1. Hello</span>

So beside the function above, I've tried this:

function parse($string){
    
    $counter = 0;
    
    $string = preg_replace_callback(("_\[b\](.*?)\[/b\]_si", function(){
        '<span class="b">'. $counter++ .'. $1</span>',
    }, $string);
}

but that, and the function at the top, didn't work. What am I doing wrong and/or could I try?

Solution

Eventually solved it with the help of TiMESPLiNTER (give him the credit!), didn't know $1 didn't get brought along and that you have to call a variable $matches in the callback function and get $matches[1] instead of $1.

$counter = 1;

function parse(){
    function cb($matches){
        global $counter;

        return '<span class="b">'. $this->counter .'. ' . $matches[1] . '</span>';
    }

    $string = preg_replace_callback("_\[b\](.*?)\[/b\]_si", 'cb', $string);
}

Answered By - Thew

Answer Checked By - Candace Johnson (PHPFixing Volunteer)