Integrating PHP and OPC

OPC PHP Code Samples

QuickOPC is unbelievably easy to use - here is a PHP example which reads and displays OPC data from a common OPC Data Access server:

 

   // Create EasyOPC-DA component
   $Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");

   // Read item value and display it
   print $Client->ReadItemValue("", "OPCLabs.KitServer", "Demo.Single");

Do you think it can be any simpler? But the simplicity is not the only advantage; the component is also very powerful. Using complex heuristic algorithms to optimize itself on the fly, it provides the most efficient, fastest access to the OPC data.

Application-side subscriptions are possible, too. The PHP example below shows how subscribe to changes of a single item and display the value of the item with each change.

   class DEasyDAClientEvents {
      function ItemChanged($varSender, $varE)
      {
         print $varE->Vtq->ToString();
         print "\n";
      }
   }

   $Client = new COM("OpcLabs.EasyOpc.DataAccess.EasyDAClient");
   $Events = new DEasyDAClientEvents();
   com_event_sink($Client, $Events, "DEasyDAClientEvents");

   $Client->SubscribeItem("", "OPCLabs.KitServer.2", "Simulation.Random", 1000);

   print "Processing item changed events for 1 minute...\n";
   for ($time = 0; $time < 60; $time++) com_message_pump(1000);

It is also easy to communicate with an OPC Unified Architecture (OPC-UA) server:

   // Instantiate the client object 
   $Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");

   // Perform the operation 
   $value = $Client->ReadValue("opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", 
      "nsu=http://test.org/UA/Data/;i=10853");

   // Display results 
   printf("Value: %s\n", $value);

---

OPC UA PubSub

The PubSub variety of OPC UA (as opposed to client-server) uses message-oriented middleware to deliver the data. QuickOPC supports it as well, as shown in the example below.

class SubscriberEvents {
    function DataSetMessage($Sender, $E)
    {
        printf("%s\n", $E);
    }
}

$SubscribeDataSetArguments = new COM("OpcLabs.EasyOpc.UA.PubSub.OperationModel.EasyUASubscribeDataSetArguments");
$ConnectionDescriptor = $SubscribeDataSetArguments->DataSetSubscriptionDescriptor->ConnectionDescriptor;
$ConnectionDescriptor->ResourceAddress->ResourceDescriptor->UrlString = "opc.udp://239.0.0.1";

$Subscriber = new COM("OpcLabs.EasyOpc.UA.PubSub.EasyUASubscriber");
$SubscriberEvents = new SubscriberEvents();
com_event_sink($Subscriber, $SubscriberEvents, "DEasyUASubscriberEvents");

$Subscriber->SubscribeDataSet($SubscribeDataSetArguments);

Tips and Tricks

• Example using ReadMultipleItems and PHP: search online forums
• Using the Event Pull Mechanism, you can enjoy the benefits of OPC subscriptions, while not having to set up event handlers (which can be problematic e.g. in context of short-lived Web request handlers).