PHP script to extract all urls from sitemap index file that contains other sitemaps

url_from_sitemap.php

<?php

// extract sitemap urls from sitemap_index.xml
$urls = array();
$xml = simplexml_load_file('https://example.com/sitemap_index.xml');
foreach ($xml->sitemap as $sitemap) {
    $sitemapUrl = (string) $sitemap->loc;
    $sitemapXml = simplexml_load_file($sitemapUrl);

    // Iterate through the URLs in the sitemap
    foreach ($sitemapXml->url as $url) {
        $urlString = (string) $url->loc;
        $urls[] = $urlString;
    }
}

print_r($urls);