Extract Easylist Adservers from the huge file for DNS

easylist_adservers.php

<?php

# Get contents from easylist domain
$content = file_get_contents('easylist.txt');

# Extract adserver list only
preg_match('/(\!\s\*\*\*\seasylist:easylist\/easylist_adservers\.txt\s\*\*\*)[^"]+(\!\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-Third\-party\sadverts\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\!)/', $content, $extracted, PREG_OFFSET_CAPTURE);

/*
 * Remove unnecessary strings from every URL
 */
$content = preg_replace('/\!\-\-\-(.*?)\-\-\-\!/', '', $extracted[0][0]);
$content = str_replace('||', '', $content);
$content = preg_replace('/\^(.*?).*/', '', $content);

# Convert list into an array for validation
$explode = explode("\n", $content);
$filteredList = [];

# Go through every url and IP then validate 
foreach($explode as $url) {
        if(filter_var('http://'.$url, FILTER_VALIDATE_URL) || filter_var('http://'.$url, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4|FILTER_FLAG_NO_PRIV_RANGE)) {
                array_push($filteredList, $url);
        }
}

# Extract unique domains from the list
$filteredList = array_unique($filteredList);

# Write result into a file for futher processing
file_put_contents('easylist_domains.txt', implode("\n", $filteredList));

?>