What is the PHP/Java bridge? ---------------------------- The PHP/Java bridge connects the PHP object system with the Java object system. For example it can be used to access java based applications running in a java application server which is running on the local host. The PHP/Java bridge communicates with the application server through local sockets using an efficient communication protocol. This means that only one JVM runs to serve all clients within a multi-process HTTP-Server. Each client process communicates with a corresponding thread spawned by the running application server. If the bridge detects that a java application server is not already running, it starts one to serve further requests. There is one example provided: test.php. You can either invoke the test.php by typing ./test.php or copy the example into the document root of you web-server and invoke the file using the browser. The PHP/Java bridge is meant as a replacement for the ext/java bridge shipped with PHP 4. It is not possible to run the build-in bridge and the PHP/Java bridge at the same time. Build and execution instructions: --------------------------------- In the directory php-java-bridge_1.x.y type: java -version # 1.3 or above (1.4.2_02 or IBM Java recommended). gcc --version # 3.2.3 or above. apachectl -version # Apache 1.3 or above. php --version # PHP 4.3.2 or above. For PHP5 see below. phpize && ./configure --with-java=/opt/IBMJava2-14 make CFLAGS="-DNDEBUG" su make install If your administrator allows you to dynamically load extensions, you can now test the extension by invoking the test.php with the command: php ./test.php. ------------------------------------ Permanently activate the module ------------------------------- It is recommended to activate the module in the global php ini file. To permanently activate the extension add the following lines to the php.ini or add a file java.ini to the directory that contains the php module descriptions (usually /etc/php.d/) with the following content: extension = java.so [java] java.log_level=5 java.log_file=/tmp/java.log # It is recommended to enable the following option and # to start a JVM as a separate process. #java.socketname=/tmp/.php_java After the module is activated, verify that the module is running by typing: echo "" | php | fgrep "java" If you want to test the extension in the web-server, you should enable the java.socketname option and start the java VM before you start the web-server. The java VM can then be started as follows JAVA_HOME= /bin/java \ -Djava.library.path= -Djava.class.path= -Djava.awt.headless=true JavaBridge For example in a gnome-terminal type: JAVA_HOME=/opt/jdk1.4 $JAVA_HOME/bin/java \ -Djava.library.path=/usr/lib/php4 \ -Djava.class.path =/usr/lib/php4 \ -Djava.awt.headless=true \ JavaBridge \ /tmp/.php_java \ 5 \ "" | tee /tmp/java.log If you are unsure how to start the java process, please look at the output of the above phpinfo() command. One of the last lines shows the command required to start the JVM. The distribution contains two scripts tested on RedHat Enterprise Linux 3. They start the JVM based on the information from phpinfo(). The "php-java-bridge" command starts the JVM and the "php-java-bridge.service" can be used on SysV based init systems to automatically start and stop the bridge as a service. This module has been tested on a Mandrake Linux System (Version 9.2), on RedHat Enterprise 3, RedHat Fedora Core 1 and 2, but it should run on all Unix-like operating systems including Solaris, Mac. However, the extension currently does not compile on systems which do not support fork()/exec(). On these systems you must disable the code in bind.c and start the java application server yourself. Fortunately all modern operating systems -- except Windows -- support fork()/exec() Other configuration options which should have been set up by the configure script but which can be changed later are: java.libpath = java.classpath = java.java_home = java.java = java.socketname= If you change the above values, please first look at the output of phpinfo() so see the original values. ------------------------------------ Using GNU Java -------------- In case you don't want to ship a JVM or JRE with your product you can use GNU gcc to compile the java part and your classes into native code. In the directory php-java-bridge_1.x.y/modules type: gcj --version # must be gcj 3.2.3 or above! gcj -fjni -oJavaBridge.srv --main=JavaBridge JavaBridge.class \ -L`pwd` -lnatcJavaBridge This creates a native executable in the current directory which does not need java anymore. It can be started with the command: ./JavaBridge.srv For example: ./JavaBridge.srv /tmp/.php_java 5 "" | tee /tmp/java.log Then point the bridge to the socket /tmp/.php_java by hard-coding the java.socketname to /tmp/.php_java (as described in the install instructions) and re-start the apache service. If you now invoke the test.php file, you should see the output from GNU Java (e.g.): ./test.php | fgrep java.vendor java.vendor -> Free Software Foundation, Inc. java.vendor.url -> http://gcc.gnu.org/java/ You can package the JavaBridge.srv and the libraries it needs (at least libnatcJavaBridge.so, libgcc_s.so.1 and libgcj.so.3, see output of ldd command) into an RPM and make sure that your client starts the JavaBridge before the httpd service gets started. -- On RedHat the init.d/httpd is started as 85/15, so it should be sufficient to start the JavaBridge executable as #84 and stop it as #16. ------------------------------------ PHP 5 support ------------- The PHP/Java bridge currently does not support the new PHP 5 object system. Zend is working with Sun Microsystems to define a standard script interface for java, please see http://www.jcp.org/en/jsr/detail?id=223 for details. When available this interface will allow PHP 5 to communicate with the JVM more efficiently; e.g. it will be possible to compile and then execute code multiple times. However, it may take some time (a few years probably) until a stable solution is available. Until an official PHP5/Java binding based on JSR-223 exists, please use PHP 4 with the PHP/Java Bridge. ------------------------------------ Dynamic module loading ---------------------- It is possible to load the bridge dynamically, for example with: However, this feature is meant for testing, only. For a production system it is recommended to compile PHP in save mode (which switches off the dl() function) and to activate all modules in the global php ini file. ------------------------------------ This module is based on the ext/java module written by Sam Ruby. His original comments follow. A few things to note: 1) new Java() will create an instance of a class if a suitable constructor is available. If no parameters are passed and the default constructor is useful as it provides access to classes like "java.lang.System" which expose most of their functionallity through static methods. 2) Accessing a member of an instance will first look for bean properties then public fields. In other words, "print $date.time" will first attempt to be resolved as "$date.getTime()", then as "$date.time"; 3) Both static and instance members can be accessed on an object with the same syntax. Furthermore, if the java object is of type "java.lang.Class", then static members of the class (fields and methods) can be accessed. 4) Exceptions raised result in PHP warnings, and null results. The warnings may be eliminated by prefixing the method call with an "@" sign. The following APIs may be used to retrieve and reset the last error: java_last_exception_get() java_last_exception_clear() 5) Overload resolution is in general a hard problem given the differences in types between the two languages. The PHP Java extension employs a simple, but fairly effective, metric for determining which overload is the best match. Additionally, method names in PHP are not case sensitive, potentially increasing the number of overloads to select from. Once a method is selected, the parameters are cooerced if necessary, possibly with a loss of data (example: double precision floating point numbers will be converted to boolean). 6) In the tradition of PHP, arrays and hashtables may pretty much be used interchangably. Note that hashtables in PHP may only be indexed by integers or strings; and that arrays of primitive types in Java can not be sparse. Also note that these constructs are passed by value, so may be expensive in terms of memory and time.