How do you use back-references to PCREs in PHP? | I read this [PHP RegEx page](http://us.php.net/manual/en/regexp.reference.php), but either I'm missing something, misreading something, or it doesn't work the way they say. I'm guessing it's one of the first two.



```
$str = preg_replace("([|]\d*)", "\1;", $str);

```