Continuously updating array with pthreads - php

Question

Im trying to make a pthreads class that continuously updates a variable that I'll be using elsewhere in the script. The pthreads class should pull the contents of a URL, assign the value to the variable, sleep and repeat.
$pair = array();
class Pair extends Thread {
public function __construct($url){
$this->url = $url;
}
public function run() {
global $pair;
while (true){
$pair = json_decode("https://btc-e.com/api/2/".$this->url."/ticker", true);
sleep(5);
}
}
}
$BTC_USD = new Pair("btc_usd");
while (true){
print_r($pair);
sleep(5);
}
$pair needs to be continuously updated and printed to the screen

Answer 1

<?php
define ('SECOND', 1000000);
class Repeater extends Thread {
public $url;
public $data;
public function __construct($url) {
$this->url = $url;
}
public function run() {
do {
/* synchronize the object */
$this->synchronized(function(){
/* fetch data into object scope */
$this->data = file_get_contents($this->url);
/* wait or quit */
if (!$this->stop)
$this->wait();
});
} while (!$this->stop);
}
public function stop() {
/* synchronize the object */
$this->synchronized(function(){
/* set stop */
$this->stop = true;
/* notify the object (could/should be waiting) */
$this->notify();
});
}
public function getData() {
/* fetch data / wait for it to arrive */
return $this->synchronized(function(){
return $this->data;
});
}
}
/* to provide a limit for the example */
$iterations = 5;
/* the url etc is not important */
$repeat = new Repeater("http://www.google.com");
$repeat->start();
/* this will only return when there is data */
while (($data = $repeat->getData())) {
var_dump(strlen($data));
$repeat->synchronized(function($repeat){
/* notify allows the thread to make he next request */
$repeat->notify();
/* waiting here for three seconds */
$repeat->wait(3 * SECOND);
}, $repeat);
if (!--$iterations) {
/* because examples should be sensible */
$repeat->stop();
break;
}
}
?>
It does not seem like a good use of resources to have a request per thread, you probably don't really want to do that in the real world. sleep is not suitable for use in multi-threading, it does not leave threads in a receptive state.
globals have no effect in the context of threading, they work as they usually do with regard to scope, but it is not inclusive of the scope of a thread.