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

Question

function parse($string){
    $counter = 0;
    
    $string = preg_replace("_\\[b\\](.*?)\\[/b\\]_si", \'\'. $counter .\'. $1&l         


        

Answer 1

You don't need to declare a global "counter" variable or design a class-based workaround. You can simply use a static variable declaration inside of preg_replace_callback()'s custom function.

Code: (Demo) -- this is the way I would code my own project

$ubbText = <<' . (++$counter) . '. ' . $m[1] . '';
         },
         $ubbText
     );

---

Alternatively, you could avoid the use of a static declaration and use preg_replace() because your code logic will not possibly replace replacements (an infinite loop is not possible). To be honest, I don't prefer this technique because it involves iterated preg_ function calls which make one replacement per iteration and the regex engine will need to restart from the beginning of the input string each time.

Code: (Demo)

$counter = 0;
do {
    $ubbText = preg_replace(
        "~\[b](.*?)\[/b]~si",
        '' . (++$counter) . '. $1',
         $ubbText,
         1,
         $count
     );
} while ($count);
echo $ubbText;

Output (from both snippets):

1. Hey
2. Hello

p.s. I suppose I should state for the record that your regex pattern will not favorably handle the possibility of nested tags [b] bold [b]re-bold[/b][/b]. If these types of occurrences are not possible in your application's text, then no worries. There are ways to mitigate this vulnerability, but I will not digress in this post. Search Stack Overflow for this if your application requires it.