php/Java bridge

What is php/Java bridge?

The php/Java bridge is an optimized, XML-based network protocol, which can be used to connect a native script engine, PHP, with a Java or ECMA 335 virtual machine. It is more than 50 times faster than local RPC via SOAP, requires less resources on the web-server side, and it is faster and more reliable than communication via the Java Native Interface.

What can I do with the php/Java bridge?

The php/Java bridge allows you to quickly access java classes from within your PHP scripts without having to know Java. It also allows you to access PHP scripts from within your Java classes without having to know PHP.

Because of this two-way flexibility, you can access hundreds of pre-built Java classes from your PHP scripts, and hundreds of pre-built PHP scripts from your Java classes opening up your applications to greater flexibility and enhanced functionality.

How it works

The php java extension and the pure PHP PHP/Java Bridge implementation use this protocol to connect running PHP instances with already running Java or .NET back ends. The communication works in both directions, the JSR 223 interface can be used to connect to a running PHP server (Apache/IIS, FastCGI, ...) so that Java components can call PHP instances and PHP scripts can invoke CLR (e.g. VB.NET, C#, COM) or Java (e.g. Java, KAWA, JRuby) based applications or transfer control back to the environment where the request came from. The bridge can be set up to automatically start the PHP front-end or the Java/.NET back end, if needed.

Each request-handling PHP process of a multi-process HTTP server communicates with a corresponding thread spawned by the VM. Requests from more than one HTTP server may either be routed to an application server running the PHP/Java Bridge back end or each HTTP server may own a PHP/Java Bridge back end and communicate with a J2EE Java application server by exchanging Java value objects; the necessary client-stub classes (e.g.: SOAP stubs or EJB client .jar files) can be loaded at run-time.

ECMA 335 based classes can be accessed if at least one back end is running inside a ECMA compliant VM, for example Novell's MONO or Microsoft's .NET. Special features such as varargs, reflection or assembly loading are also supported.

When the back end is running in a J2EE environment, session sharing between PHP and JSP is always possible. Clustering and load balancing is available if the J2EE environment supports these features.

The PHP/Java Bridge does not use the Java Native Interface ("JNI"). PHP instances are allocated from the HTTP (Apache/IIS) pool, instances of Java/J2EE components are allocated from the back end. The allocated instances communicate using a "continuation passing style", see java_closure() and the invocable interface. In case a PHP instance crashes, it will not take down the Java application server or servlet engine.