How to start writing a PHP5 extension in C++

Question

I'm writing a PHP5 extension, and while I could write it in C, it would be easier to use C++ and take advantage of the STL and Boost.

Trouble is, the tutorials I've seen only deal with C, and I'm looking for a basic example which uses C++

Here's what I've tried so far:

config.m4

[ --enable-hello   Enable Hello World support])

if test "$PHP_HELLO" = "yes"; then
  AC_DEFINE(HAVE_HELLO, 1, [Whether you have Hello World])
  PHP_NEW_EXTENSION(hello, hello.cpp, $ext_shared)
fi

php_hello.h

Note my attempt to declare the bits that PHP interfaces with as extern "C"

#ifndef PHP_HELLO_H
#define PHP_HELLO_H 1


extern "C" {

#define PHP_HELLO_WORLD_VERSION "1.0"
#define PHP_HELLO_WORLD_EXTNAME "hello"

PHP_FUNCTION(hello_world);

extern zend_module_entry hello_module_entry;
#define phpext_hello_ptr &hello_module_entry

}
#endif

hello.cpp

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "php.h"
#include "php_hello.h"

static function_entry hello_functions[] = {
    PHP_FE(hello_world, NULL)

    {NULL, NULL, NULL}
};

zend_module_entry hello_module_entry = {
#if ZEND_MODULE_API_NO >= 20010901
    STANDARD_MODULE_HEADER,
#endif
    PHP_HELLO_WORLD_EXTNAME,
    hello_functions,
    NULL,
    NULL,
    NULL,
    NULL,
    NULL,
#if ZEND_MODULE_API_NO >= 20010901
    PHP_HELLO_WORLD_VERSION,
#endif
    STANDARD_MODULE_PROPERTIES
};

#ifdef COMPILE_DL_HELLO
ZEND_GET_MODULE(hello)
#endif

PHP_FUNCTION(hello_world)
{
    RETURN_STRING("Hello World", 1);
}

....and here are my build errors:

If I phpize, configure and make this, I get the following (reformatted for clarity)

$ make
/bin/bash /home/paul/php5/php-5.2.8/ext/hello2/libtool 
   --mode=compile  
   -I. 
   -I/home/paul/php5/php-5.2.8/ext/hello2 -DPHP_ATOM_INC 
   -I/home/paul/php5/php-5.2.8/ext/hello2/include 
   -I/home/paul/php5/php-5.2.8/ext/hello2/main 
   -I/home/paul/php5/php-5.2.8/ext/hello2 
   -I/usr/local/include/php 
   -I/usr/local/include/php/main 
   -I/usr/local/include/php/TSRM 
   -I/usr/local/include/php/Zend 
   -I/usr/local/include/php/ext 
   -I/usr/local/include/php/ext/date/lib  
   -DHAVE_CONFIG_H     
   -c /home/paul/php5/php-5.2.8/ext/hello2/hello.cpp 
   -o hello.lo 
libtool: compile: unrecognized option `-I.'
libtool: compile: Try `libtool --help' for more information.
make: *** [hello.lo] Error 1

I suspect I need more work doing to the config.m4 in order to create a working makefile but I'm pretty new to the GCC toolchain.

If it helps, I'm only targetting php 5.2.6+, and only on Linux (specifically, Ubuntu 8.04). My build environment is using Ubuntu 8.10, using gcc 4.3.2

Pointers gratefully received!

Answer 1

After posting I came across CodeGen_PECL which creates a skeleton extension from an XML based description of the extension. This includes a tag make it output C++

As well as making sure the header file used extern "C", the generated cpp file also ensured the ZEND_GET_MODULE(hello) was inside an extern "C" block also.

As expected, the biggest difference was in the m4 file, which looked like this:

dnl
dnl $ Id: $
dnl

PHP_ARG_ENABLE(hello, whether to enable hello functions,
[  --enable-hello         Enable hello support])

if test "$PHP_HELLO" != "no"; then
  PHP_REQUIRE_CXX
  AC_LANG_CPLUSPLUS
  PHP_ADD_LIBRARY(stdc++,,HELLO_SHARED_LIBADD)
  export OLD_CPPFLAGS="$CPPFLAGS"
  export CPPFLAGS="$CPPFLAGS $INCLUDES -DHAVE_HELLO"

  AC_MSG_CHECKING(PHP version)
  AC_TRY_COMPILE([#include <php_version.h>], [
#if PHP_VERSION_ID < 40000
#error  this extension requires at least PHP version 4.0.0
#endif
],
[AC_MSG_RESULT(ok)],
[AC_MSG_ERROR([need at least PHP 4.0.0])])

  export CPPFLAGS="$OLD_CPPFLAGS"


  PHP_SUBST(HELLO_SHARED_LIBADD)
  AC_DEFINE(HAVE_HELLO, 1, [ ])

  PHP_NEW_EXTENSION(hello, hello.cpp , $ext_shared)

fi

So, if you're struggling with the same problem, use CodeGen_PECL, or adapt the m4 sample above (as well as making sure you've used extern "C" in your header and around the ZEND_GET_MODULE macro)

Answer 2

There's also this quickie intro to wrapping a class (and exporting functions in Class::Method style) here: http://devzone.zend.com/article/4486

For me the most useful part is the lines to add for C++ compiler/linking rules to config.m4 for phpize.