curl_multi_add_handle

The 'do' loop in this example will cycle indefinitely until all curl downloads complete, needlessly using CPU cycles. A much better way is to block while dowloads are in progress. Refer to the example code on the curl_multi_exec() page instead, which does this!

Sometime with arrays and loops (i.e. for or do while or foreach) curl_multi_init loses some hits, to work around this problem it is necessary to divide the loop into two parts: the start with key number zero and than, all the rest. In this way the curl_multi_init doesn't lose any hits. I did a lot of test and it seems to work well enough. 
<?php
function set_option($x, $y){
curl_setopt($x, CURLOPT_URL, $y);
curl_setopt($x, CURLOPT_HEADER, 0);
curl_setopt($x, CURLOPT_FOLLOWLOCATION, TRUE);
curl_setopt($x, CURLOPT_RETURNTRANSFER, TRUE);
curl_setopt($x, CURLOPT_ENCODING, "gzip,deflate");
}
$nodes = array('http://php.net/manual/it/function.curl-multi-add-handle.php', 
'http://php.net/manual/en/function.curl-multi-init.php', 
'http://php.net/manual/en/function.curl-multi-setopt.php'
);
$node_count = count($nodes);
$curl_arr = array();
$master = curl_multi_init();
/*
now I put the first part of the array with the start key number zero, add all 
options and add the curl_multi_add_handle; 
it is necessary to detach this first part to avoid to lose some handles and than running 
 the loop with the start key number one. 
In this way the curl_multi_init doesn't lose anything and seems to be very stable. 
*/ 
 $curl_arr[0] = curl_init($nodes[0]);
 set_option($curl_arr[0], $nodes[0]);
 curl_multi_add_handle($master, $curl_arr[0]);
 
/* 
now the loop can start with key number one 
*/
$i = 1;
do {
 if ($i!==0){
 
 $curl_arr[$i] = curl_init($nodes[$i]);
 set_option($curl_arr[$i], $nodes[$i]);
 curl_multi_add_handle($master, $curl_arr[$i]);
 }
$i++; 
}while($i < $node_count);
$running = NULL;
do {
 curl_multi_exec($master,$running);
} while($running);
$results = array();
$q = 0;
do{
 $results[$q] = curl_multi_getcontent($curl_arr[$q]);
 curl_multi_remove_handle($master, $curl_arr[$q]);
$q++; 
}while($q < $node_count);
foreach($results as $value){
 echo $value;
}
?>

$nodes = array('http://www.google.com', 'http://www.microsoft.com', 'http://yahoo.com');
$node_count = count($nodes);
$curl_arr = array();
$master = curl_multi_init();
for($i = 0; $i < $node_count; $i++)
{
 $url =$nodes[$i];
 $curl_arr[$i] = curl_init($url);
 curl_setopt($curl_arr[$i], CURLOPT_RETURNTRANSFER, true);
 curl_multi_add_handle($master, $curl_arr[$i]);
}
do {
 curl_multi_exec($master,$running);
} while($running > 0);
echo "results: ";
for($i = 0; $i < $node_count; $i++)
{
 $results = curl_multi_getcontent ( $curl_arr[$i] );
 echo( $i . "\n" . $results . "\n");
}
echo 'done';