php: dynamic preg_replace

Question

The code below is not a functioning method it's just written to help you understand what I'm trying to do.


// $i = occurrence to replace
// $r = content to replace

private function inject($i, $r) {
      // regex matches anything in the format {value|:value}
      $output = preg_replace('/\{(.*?)\|\:(.*?)\}/', '$r', $this->source);
      $output[$i]
}

How do I find the $i occurrence in $output; and replace it with $r;?

Note: All I want to do is use $i (which is a number) to find the occurrence of that nmber in a preg_replace; For exmaple: I might want to replace the second occurrence of the preg_replace pattern with the variable $r

The occurrence number of the matched item. $i for example could be 1 then, regex needs to find the 1 occurence and replace it with $r; — kr1zmo
– kr1zmo, Commented Apr 1, 2011 at 22:00

mario · Accepted Answer · 2011-04-01 22:10:20Z

1

I think you can only accomplish such an occurence counting with a callback:

private function inject($i, $r) {
      $this->i = $i;
      $this->r = $r;

      // regex matches anything in the format {value|:value}
      $output = preg_replace_callback('/\{(.*?)\|\:(.*?)\}/',
                array($this, "inject_cb"), $this->source);
}

function inject_cb($match) {
    if ($this->i --) {
        return $match[0];
    }
    else {
        return $this->r;
    }
}

It leaves the first $i matches as is, and uses the tempoary $this->r once when the countdown is matched. Could be done with a closure to avoid ->$i and ->$r however.

answered Apr 1, 2011 at 22:10

mario

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3 Comments

kr1zmo Over a year ago

Can't seem to get this working? I'm sure it is probably an error on my part.

mario Over a year ago

It needs to do something with $output still. An alternative option for this task would be preg_split with PREG_SPLIT_DELIM_CAPTURE maybe (but more fiddly).

ridgerunner Over a year ago

I think these two functions need to be wrapped inside a class (as methods) for this to work.

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