Get all the URLs using multi curl

I'm working on an app that gets all the URLs from an array of sites and displays it in array form or JSON.

I can do it using for loop, the problem is the execution time when I tried 10 URLs it gives me an error saying exceeds maximum execution time.

Upon searching I found this multi curl

I also found this Fast PHP CURL Multiple Requests: Retrieve the content of multiple URLs using CURL. I tried to add my code but didn't work because I don't how to use the function.

Hope you help me.

Thanks.

This is my sample code.

<?php

$urls=array(
'http://site1.com/',
'http://site2.com/',
'http://site3.com/');


$mh = curl_multi_init();
foreach ($urls as $i => $url) {

        $urlContent = file_get_contents($url);

        $dom = new DOMDocument();
        @$dom->loadHTML($urlContent);
        $xpath = new DOMXPath($dom);
        $hrefs = $xpath->evaluate("/html/body//a");

        for($i = 0; $i < $hrefs->length; $i++){
            $href = $hrefs->item($i);
            $url = $href->getAttribute('href');
            $url = filter_var($url, FILTER_SANITIZE_URL);
            // validate url
            if(!filter_var($url, FILTER_VALIDATE_URL) === false){
                echo '<a href="'.$url.'">'.$url.'</a><br />';
            }
        }

        $conn[$i]=curl_init($url);
        $fp[$i]=fopen ($g, "w");
        curl_setopt ($conn[$i], CURLOPT_FILE, $fp[$i]);
        curl_setopt ($conn[$i], CURLOPT_HEADER ,0);
        curl_setopt($conn[$i],CURLOPT_CONNECTTIMEOUT,60);
        curl_multi_add_handle ($mh,$conn[$i]);
}
do {
    $n=curl_multi_exec($mh,$active);
}
while ($active);
foreach ($urls as $i => $url) {
    curl_multi_remove_handle($mh,$conn[$i]);
    curl_close($conn[$i]);
    fclose ($fp[$i]);
}
curl_multi_close($mh);
?>

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