One month ago I posted an article called Building a simple HTTP client with PHP. A REST client. In this post I tried to create a simple fluid interface to call REST webservices in PHP. Some days ago I read an article and one light switch on on my mind. I can use curl’s “multi” functions to improve my library and perform simultaneous calls very easily.

I’ve got a project that needs to call to different webservices. Those webservices sometimes are slow (2-3 seconds). If I need to call to, for example, three webservices my script will use the add of every single call’s time. With this improve to the library I will use only the time of the slowest webservice. 2 seconds instead of 2+2+2 seconds. Great.

For the example I’ve created a really complex php script that sleeps x seconds depend on an input param:

sleep((integer) $_REQUEST['sleep']);
echo $_REQUEST['sleep'];

With synchronous calls:

echo Http::connect('localhost', 8082)
    ->doGet('/tests/gam_http/sleep.php', array('sleep' => 3));
echo Http::connect('localhost', 8082)
    ->doPost('/tests/gam_http/sleep.php', array('sleep' => 2));
echo Http::connect('localhost', 8082)
    ->doGet('/tests/gam_http/sleep.php', array('sleep' => 1));

This script takes more or less 6 seconds (3+2+1)

But If I switch it to:

$out = Http::connect('localhost', 8082)
    ->get('/tests/gam_http/sleep.php', array('sleep' => 3))
    ->post('/tests/gam_http/sleep.php', array('sleep' => 2))
    ->get('/tests/gam_http/sleep.php', array('sleep' => 1))
    ->run();
print_r($out);

The script only uses 3 seconds (the slowest process)

I’ve got a project that uses it. But I have a problem. I have webservices in different hosts so I’ve done a bit change to the library:

$out = Http::multiConnect()
    ->add(Http::connect('localhost', 8082)->get('/tests/gam_http/sleep.php', array('sleep' => 3)))
    ->add(Http::connect('localhost', 8082)->post('/tests/gam_http/sleep.php', array('sleep' => 2)))
    ->add(Http::connect('localhost', 8082)->get('/tests/gam_http/sleep.php', array('sleep' => 1)))
    ->run();

With a single connection, the exceptions are easy to implement. If curl_getinfo() returns an error message I throw an exception, but now with a multiple interface how I can do it? I throw an exception if one call fail, or not? I have decided not to use exceptions in multiple interface. I always return an array with all the output of every webservice’s call and if something wrong happens instead of the output I will return an instance of Http_Multiple_Error class. Why I use a class instead of a error message? The answer is easy. If I want to check all the answers I can check if any of them is an instanceof Http_Multiple_Error. Also I don’t want to check anything I put a silentMode() function to switch off all error messages.

$out = Http::multiConnect()
    ->silentMode()
    ->add(Http::connect('localhost', 8082)->get('/tests/gam_http/sleep.php', array('sleep' => 3)))
    ->add(Http::connect('localhost', 8082)->post('/tests/gam_http/sleep.php', array('sleep' => 2)))
    ->add(Http::connect('localhost', 8082)->get('/tests/gam_http/sleep.php', array('sleep' => 1)))
    ->run();

The full code is available on google code but the main function is the following one:

    ...
    private function _run()
    {
        $headers = $this->_headers;
        $curly = $result = array();

        $mh = curl_multi_init();
        foreach ($this->_requests as $id => $reg) {
            $curly[$id] = curl_init();

            $type     = $reg[0];
            $url       = $reg[1];
            $params = $reg[2];

            if(!is_null($this->_user)){
               curl_setopt($curly[$id], CURLOPT_USERPWD, $this->_user.':'.$this->_pass);
            }

            switch ($type) {
                case self::DELETE:
                    curl_setopt($curly[$id], CURLOPT_URL, $url . '?' . http_build_query($params));
                    curl_setopt($curly[$id], CURLOPT_CUSTOMREQUEST, self::DELETE);
                    break;
                case self::POST:
                    curl_setopt($curly[$id], CURLOPT_URL, $url);
                    curl_setopt($curly[$id], CURLOPT_POST, true);
                    curl_setopt($curly[$id], CURLOPT_POSTFIELDS, $params);
                    break;
                case self::GET:
                    curl_setopt($curly[$id], CURLOPT_URL, $url . '?' . http_build_query($params));
                    break;
            }
            curl_setopt($curly[$id], CURLOPT_RETURNTRANSFER, true);
            curl_setopt($curly[$id], CURLOPT_HTTPHEADER, $headers);

            curl_multi_add_handle($mh, $curly[$id]);
        }

        $running = null;
        do {
            curl_multi_exec($mh, $running);
            sleep(0.2);
        } while($running > 0);

        foreach($curly as $id => $c) {
            $status = curl_getinfo($c, CURLINFO_HTTP_CODE);
            switch ($status) {
                case self::HTTP_OK:
                case self::HTTP_CREATED:
                case self::HTTP_ACEPTED:
                    $result[$id] = curl_multi_getcontent($c);
                    break;
                default:
                    if (!$this->_silentMode) {
                        $result[$id] = new Http_Multiple_Error($status, $type, $url, $params);
                    }
            }
            curl_multi_remove_handle($mh, $c);
        }

        curl_multi_close($mh);
        return $result;

The problem:

I’ve got a class library in PHP. This class library is distributed in a several servers and I want to call them synchronously. The class library has a XMLRPC interface with Zend Framework XMLRPC server.
There is an example class

class Gam_Dummy
{
    /**
     * foo
     *
     * @param integer $arg1
     * @param integer $arg2
     * @return integer
     */
    function foo($arg1, $arg2)
    {
        return $arg1 + $arg2;
    }
}

and the xmlrpc server:

$class = (string) $_GET['class'];
$server = new Zend_XmlRpc_Server();
$server->setClass($class);
echo $server->handle();

First solution

An easy a fast solution for calling remote interfaces is:

$class = "Gam_Dummy";
$client = new Zend_XmlRpc_Client("http://location/of/xmlrpc/server?class={class}");
echo $client->call('foo', array($arg1, $arg2));

and if we have several remote servers:

$servers = array(
    'server1' => 'http://location/of/xmlrpc/server1',
    'server2' => 'http://location/of/xmlrpc/server2',
    'server3' => 'http://location/of/xmlrpc/server3'
    );

$class = "Gam_Dummy";
foreach (array_values($servers) as $_server) {
    $server = "{_server}?class={$class}";
    $client = new Zend_XmlRpc_Client($server);
    echo $client->call('foo', array($arg1, $arg2));
}

Second solution (one remote server):

I want to use the following interface to call my remote class

$class = "Gam_Dummy";
Gam_Dummy::remote("Gam_Dummy", 'server1')->foo($arg1, $arg2);

Why? The answer is because I like to coding with the help of the IDE. If I use the first solution I must remember Gam_Dummy class has a foo function with two parameters. With the second solution if I place the PHPDoc code correctly my IDE will help me showing me the function list of the Gam_Dummy class and even when I type Gam_ IDE will show me all the classes of my repository starting with Gam_. That issue could sound irrelevant for a lot of people but for me is really useful

To get this interface I will change my Gam_Dummy class to:

class Gam_Dummy
{
    /**
     * foo
     *
     * @param integer $arg1
     * @param integer $arg2
     * @return integer
     */
    function foo($arg1, $arg2)
    {
        return $arg1 + $arg2;
    }

    /**
     * Remote interface
     *
     * @param string|array $server
     * @return Gam_Dummy
     */
    static function remote($server)
    {
        return new Remote(get_called_class(), $server);
    }
}

And of course Remote class:

class Remote
{
    private $_class  = null;
    private $_server = null;

    function __construct($class, $server)
    {
        $this->_class  = $class;
        $this->_server = $server;
    }

    function __call($method, $arguments)
    {
        if (class_exists($this->_class)) {
            $server = "{$this->_server}?class={$this->_class}";
            $client = new Zend_XmlRpc_Client($server);
            return $client->call($method, array($arg1, $arg2));
        }
    }
}

Cool. Isn’t it?. But there is a problem if I want to work with two or more remote servers I must write one line of code for each server:

Gam_Dummy::remote('http://location/of/xmlrpc/server1')->foo($arg1, $arg2);
Gam_Dummy::remote('http://location/of/xmlrpc/server2')->foo($arg1, $arg2);
Gam_Dummy::remote('http://location/of/xmlrpc/server3')->foo($arg1, $arg2);

or may better with the array $servers

foreach (array_values($servers) as $server) {
    Gam_Dummy::remote($server)->foo($arg1, $arg2);
}

Third solution for multiple remote servers:

I would like to use this interface instead of solution two with a foreach for multiple servers:

$servers = array(
    'server1' => 'http://location/of/xmlrpc/server1',
    'server2' => 'http://location/of/xmlrpc/server2',
    'server3' => 'http://location/of/xmlrpc/server3'
    );

Gam_Dummy::remote($servers)->foo($arg1, $arg2);

so I change Remote class to:

class Remote
{
    private $_class  = null;
    private $_server = null;

    function __construct($class, $server)
    {
        $this->_class  = $class;
        $this->_server = $server;
    }

    function __call($method, $arguments)
    {
        $out = array();
        if (is_array($this->_server)) {
            foreach ($this->_server as $key => $_server) {
                $server = "{$_server}?class={$this->_class}";
                $client = new Zend_XmlRpc_Client($server);
                $out[$key] = $client->call($method, $arguments);
            }
        } else {
            $server = "{$this->_server}?class={$this->_class}";
            $client = new Zend_XmlRpc_Client($server);
            $out = $client->call($method, $arguments);
        }
        return $out;
    }
}