There are two possible ways to bridge PHP and
Java: you can either integrate PHP into a Java
Servlet environment, which is the more stable and
efficient solution, or integrate Java support into PHP.
The former is provided by a SAPI module that interfaces
with the Servlet server, the latter by this Java
extension.
The Java extension provides a simple and effective
means for creating and invoking methods on Java objects
from PHP. The JVM is created using JNI, and everything
runs in-process.
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To include Java support in your PHP build you must
add the option
--with-java[=DIR] where DIR points to the base
install directory of your JDK. This extension can only
be built as a shared dl. More build instructions for
this extension can be found in
php4/ext/java/README.
Note to Win32 Users: In order to enable this module on a Windows environment, you must copy jvm.dll from the DLL folder of the PHP/Win32 binary package to the SYSTEM32 folder of your windows machine. (Ex:C:\WINNT\SYSTEM32 or C:\WINDOWS\SYSTEM32)
php.ini中的設定會影響這些函數的行為。
表格 1. Java configuration options
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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.
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.
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.
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:
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).
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.
The Java Servlet SAPI builds upon the mechanism
defined by the Java extension to enable the entire PHP
processor to be run as a servlet. The primary
advanatage of this from a PHP perspective is that web
servers which support servlets typically take great
care in pooling and reusing JVMs. Build instructions
for the Servlet SAPI module can be found in php4/sapi/README. Notes:
While this code is intended to be able to run
on any servlet engine, it has only been tested on
Apache's Jakarta/tomcat to date. Bug reports,
success stories and/or patches required to get this
code to run on other engines would be
appreciated.
PHP has a habit of changing the working
directory. sapi/servlet will eventually change it
back, but while PHP is running the servlet engine
may not be able to load any classes from the
CLASSPATH which are specified using a relative
directory syntax, or find the work directory used
for administration and JSP compilation tasks.