PHP ASN to Ranges with Info, to Serialized Array

<?php
/**
 * Get CIDRs from Robtex, per ASN
 */
$output = array();
#400000
for($i = 0; $i<=400000; $i++)
{
    $data = @file_get_contents('https://www.robtex.com/as/as'.$i.'.html');

    preg_match('/<title>(.*)<\/title>/', $data, $ASN_title);
    preg_match_all('/[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}\/[0-9]{2}/', $data, $ASN_ranges);

    if(count($ASN_title)<1)
    {
        continue;
    }

    foreach($ASN_ranges[0] as $range)
    {
        $return[$ASN_title[1]][] = $range;
    }
    $output[] = $return;
    unset($return);
}

file_put_contents('output.txt', serialize($output));