create indexed array inside preg_replace_callback function - php

Question

I have simple code to replace links in text with numbers 1 to whatever the number of links in text is.
echo preg_replace_callback('/regex/',
function ($links) {
$reg = "/regex/i";
preg_match($reg, $links[0], $url);
static $count = 1;
return '['. $count++ .']';
}, $html);
This is working ok. Now I want to add same number if same links are used in text more times. What I came up with is to create indexed array and inside the function compare current link to existing links in array. If same is found then already indexed link is used along with index number(which will be the link number in text) .
Problem: when I create and add urls to index inside function like this:
$arr=array();
$array[] = $url[0];
var_dump($arr) shows all links with same index number 0. How can I solve this? Thank you.

Answer 1

You are probably getting this if you declare your array inside the callback as this function is called once for each item and so doesn't remember previous values.
One simple way is to define the array outside and use() the value in your callback, which allows the function to access the variable outside it's scope...
$arr=array();
echo preg_replace_callback('/regex/',
function ($links) use (&$arr) {
$reg = "/regex/i";
preg_match($reg, $links[0], $url);
if ( isset($arr[$url[0]]) ) {
$count = ++$arr[$url[0]];
}
else {
$count = 0;
$arr[$url[0]] = $count;
}
return '['. $count++ .']';
}, $html);
Mandatory Note: (for me anyway) processing HTML/XML is usually better done using something like DOMDocument as it can understand both the structure and semantics of the document.