cURL Multi Threading? - php

Question

I've heard a lot about php's multi threading with cURL but have never really tried it and I find it a bit tough to understand how it actually works. Could anyone convert this into curl_multi?
$path1 = array("path1", "path2", "path3"); //example
$path2 = array("path1", "path2", "path3"); //example
$opt = curl_init($path1);
curl_setopt($opt, CURLOPT_RETURNTRANSFER, true);
$content = curl_exec($opt);
curl_close($opt);
file_put_contents($path2, $content);
What I want to actually do is to download multiple files from the arrays path 1 into path 2 using curl_multi.

Answer 1

This is nice project to start with...
https://github.com/jmathai/php-multi-curl
I am using curl multi and it is awesome indeed. I am using this to make faster push notifications.
https://github.com/Krutarth/FlashSnsPns

Answer 2

The above accepted answer is outdated/wrong, So, correct answer has to be up voted.
http://php.net/manual/en/function.curl-multi-init.php
Now, PHP supports fetching multiple URLs at the same time.
There is a very good function written by someone, http://archevery.blogspot.in/2013/07/php-curl-multi-threading.html
This is the function:
function runRequests($url_array, $thread_width = 4) {
$threads = 0;
$master = curl_multi_init();
$curl_opts = array(CURLOPT_RETURNTRANSFER => true,
CURLOPT_FOLLOWLOCATION => true,
CURLOPT_MAXREDIRS => 5,
CURLOPT_CONNECTTIMEOUT => 15,
CURLOPT_TIMEOUT => 15,
CURLOPT_RETURNTRANSFER => TRUE);
$results = array();
$count = 0;
foreach($url_array as $url) {
$ch = curl_init();
$curl_opts[CURLOPT_URL] = $url;
curl_setopt_array($ch, $curl_opts);
curl_multi_add_handle($master, $ch); //push URL for single rec send into curl stack
$results[$count] = array("url" => $url, "handle" => $ch);
$threads++;
$count++;
if($threads >= $thread_width) { //start running when stack is full to width
while($threads >= $thread_width) {
usleep(100);
while(($execrun = curl_multi_exec($master, $running)) === -1){}
curl_multi_select($master);
// a request was just completed - find out which one and remove it from stack
while($done = curl_multi_info_read($master)) {
foreach($results as &$res) {
if($res['handle'] == $done['handle']) {
$res['result'] = curl_multi_getcontent($done['handle']);
}
}
curl_multi_remove_handle($master, $done['handle']);
curl_close($done['handle']);
$threads--;
}
}
}
}
do { //finish sending remaining queue items when all have been added to curl
usleep(100);
while(($execrun = curl_multi_exec($master, $running)) === -1){}
curl_multi_select($master);
while($done = curl_multi_info_read($master)) {
foreach($results as &$res) {
if($res['handle'] == $done['handle']) {
$res['result'] = curl_multi_getcontent($done['handle']);
}
}
curl_multi_remove_handle($master, $done['handle']);
curl_close($done['handle']);
$threads--;
}
} while($running > 0);
curl_multi_close($master);
return $results;
}
You can just use it.