how to access a variable from a class using php extension?

Question

I am working in c++ under ubuntu. I have the following example: [car.h]

#ifndef VEHICLES_CAR_H
#define VEHICLES_CAR_H

// A very simple car class
class Car {
public:
    Car();
    void shift(int gear);
    bool accelerate();
    void brake();
    int getCurrentSpeed();
    int getCurrentGear();
public:
    int maxGear;
    int currentGear;
    int speed;
};

#endif /* VEHICLES_CAR_H *

/ [car.cc]

#include "car.hpp"
#include "car2.hpp"
#include "car2.cc"
#include "car3.h"
#include "car3.cc"
#include <stdio.h>
#include <iostream>
using namespace std;

Car::Car() {

}

void Car::shift(int gear) {
    if (gear < 1 || gear > maxGear) {
        return;
    }
    currentGear = gear;
}
bool Car::accelerate() {
    speed = 10;
    if (speed == 10) return true;
    else return false;
}

void Car::brake() {
    speed -= (5 *5);
}

int Car::getCurrentSpeed() {
    Hello h; //this is in another class...it's working ok
    h.say_hello();
    speed=5;
    return speed;
}

int Car::getCurrentGear() {
    return currentGear;
}

[vehicles.cc]

#include "php_vehicles.h"
#include "car.hpp"

zend_object_handlers car_object_handlers;

struct car_object {
    zend_object std;
    Car *car;
};

zend_class_entry *car_ce;

void car_free_storage(void *object TSRMLS_DC)
{
    car_object *obj = (car_object *)object;
    delete obj->car; 

    zend_hash_destroy(obj->std.properties);
    FREE_HASHTABLE(obj->std.properties);

    efree(obj);
}

zend_object_value car_create_handler(zend_class_entry *type TSRMLS_DC)
{
    zval *tmp;
    zend_object_value retval;

    car_object *obj = (car_object *)emalloc(sizeof(car_object));
    memset(obj, 0, sizeof(car_object));
    obj->std.ce = type;

    ALLOC_HASHTABLE(obj->std.properties);
    zend_hash_init(obj->std.properties, 0, NULL, ZVAL_PTR_DTOR, 0);
    zend_hash_copy(obj->std.properties, &type->default_properties,
        (copy_ctor_func_t)zval_add_ref, (void *)&tmp, sizeof(zval *));

    retval.handle = zend_objects_store_put(obj, NULL,
        car_free_storage, NULL TSRMLS_CC);
    retval.handlers = &car_object_handlers;

    return retval;
}


PHP_METHOD(Car, __construct)
{
    long maxGear;
    Car *car = NULL;
    zval *object = getThis();

    if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "", NULL) == FAILURE) {
        RETURN_NULL();
    }

    car = new Car();
    car_object *obj = (car_object *)zend_object_store_get_object(object TSRMLS_CC);
    obj->car = car;

}
PHP_METHOD(Car, shift)
{
}
PHP_METHOD(Car, accelerate)
{
    Car *car;
    car_object *obj = (car_object *)zend_object_store_get_object(
        getThis() TSRMLS_CC);
    car = obj->car;
    if (car != NULL) {
       RETURN_BOOL( car->accelerate());
       RETURN_LONG(car->speed);
    }

}
PHP_METHOD(Car, brake)
{
}
PHP_METHOD(Car, getCurrentSpeed)
{
    Car *car;
    car_object *obj = (car_object *)zend_object_store_get_object(
        getThis() TSRMLS_CC);
    car = obj->car;
    if (car != NULL) {
        RETURN_LONG(car->getCurrentSpeed());
    }
    RETURN_NULL();

}
PHP_METHOD(Car, getCurrentGear)
{
}

function_entry car_methods[] = {
    PHP_ME(Car,  __construct,     NULL, ZEND_ACC_PUBLIC | ZEND_ACC_CTOR)
    PHP_ME(Car,  shift,           NULL, ZEND_ACC_PUBLIC)
    PHP_ME(Car,  accelerate,      NULL, ZEND_ACC_PUBLIC)
    PHP_ME(Car,  brake,           NULL, ZEND_ACC_PUBLIC)
    PHP_ME(Car,  getCurrentSpeed, NULL, ZEND_ACC_PUBLIC)
    PHP_ME(Car,  getCurrentGear,  NULL, ZEND_ACC_PUBLIC)
    {NULL, NULL, NULL}
};

PHP_MINIT_FUNCTION(vehicles)
{
   zend_class_entry ce;
    INIT_CLASS_ENTRY(ce, "Car", car_methods);
    car_ce = zend_register_internal_class(&ce TSRMLS_CC);
    car_ce->create_object = car_create_handler;
    memcpy(&car_object_handlers,
        zend_get_std_object_handlers(), sizeof(zend_object_handlers));
    car_object_handlers.clone_obj = NULL;
    return SUCCESS;

}

zend_module_entry vehicles_module_entry = {
#if ZEND_MODULE_API_NO >= 20010901
    STANDARD_MODULE_HEADER,
#endif
    PHP_VEHICLES_EXTNAME,
    NULL,        /* Functions */
    PHP_MINIT(vehicles),        /* MINIT */
    NULL,        /* MSHUTDOWN */
    NULL,        /* RINIT */
    NULL,        /* RSHUTDOWN */
    NULL,        /* MINFO */
#if ZEND_MODULE_API_NO >= 20010901
    PHP_VEHICLES_EXTVER,
#endif
    STANDARD_MODULE_PROPERTIES
};

#ifdef COMPILE_DL_VEHICLES
extern "C" {
ZEND_GET_MODULE(vehicles)
}
#endif

[php_vehicles.h]

  #ifndef PHP_VEHICLES_H
#define PHP_VEHICLES_H

#define PHP_VEHICLES_EXTNAME  "vehicles"
#define PHP_VEHICLES_EXTVER   "0.1"

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

#ifdef __cplusplus
extern "C" {
    #endif
#ifdef ZTS
#include "TSRM.h"
#endif
#ifdef __cplusplus
}
#endif

#ifdef __cplusplus
extern "C" {
    #endif
#include "php.h"

#ifdef __cplusplus
}
#endif


extern zend_module_entry vehicles_module_entry;
#define phpext_vehicles_ptr &vehicles_module_entry;

#endif /* PHP_VEHICLES_H */

[config.m4]

    PHP_ARG_ENABLE(vehicles,
    [Whether to enable the "vehicles" extension],
    [  --enable-vehicles      Enable "vehicles" extension support])

if test $PHP_VEHICLES != "no"; then
    PHP_REQUIRE_CXX()
    PHP_SUBST(VEHICLES_SHARED_LIBADD)
    PHP_ADD_LIBRARY(stdc++, 1, VEHICLES_SHARED_LIBADD)
    PHP_NEW_EXTENSION(vehicles, vehicles.cc car.cc, $ext_shared)
fi

[test.php]

<html>
    <head>
        <title>MY FIRST PHP EXTENSION</title>
    </head>
    <body>
<?php


$car = new Car();
echo "FIRST RESULT: ".$car->getCurrentSpeed()." ";  // prints '0'
//echo "CAR IS: ".$car->accelerate();
if ($car->accelerate() == True) { echo "IT IS TRUE AND SPEED IS: ". $car->$speed;}

//echo "SECOND RESULT: ". $car->getCurrentSpeed()." "; // prints '5'
?>

    </body>
</html>

I have the following error at line $car->$speed:  Undefined variable: speed in /home/test.php on line 13
PHP Fatal error:  Cannot access empty property

WHY? How to solve this? thx ! appreciate

qbert220 · Accepted Answer · 2011-09-13 07:30:30Z

1

Change $car->$speed to $car->getCurrentSpeed():

if ($car->accelerate() == True) { echo "IT IS TRUE AND SPEED IS: ". $car->getCurrentSpeed();}

answered Sep 13, 2011 at 7:30

qbert220

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5 Comments

sunset Over a year ago

what if i would like to print the speed - the variable and not the function. How to solve this? THX!

qbert220 Over a year ago

The method gets the current value of speed (from the C++ class). I don't believe it is possible to access the c++ variable directly from PHP. You need to have getter and setter methods in your c++ class to allow access to variables from PHP. Your getCurrentSpeed method should just contain return speed;.

sunset Over a year ago

i see. So if I want to print all the variables from the Car class is there a possible way to print them all in one function?(what to do to print speed, currentGear and maxGear in a single method)?

qbert220 Over a year ago

Call all the getter methods from PHP and echo the values returned. Alternatively add a new c++ method that returns a string to PHP containing everything to be echoed.

sunset Over a year ago

qbert i would like to ask you: if the class Car was inside a class Machines like: class Machines {class Car.....}; what should i change in my vehicles.cc code? please help

s.webbandit · Accepted Answer · 2011-09-13 08:01:47Z

0

Calling $car->$speed property you should firs define $speed variable.

$speed = 'speed'; // You should define this in PHP code before calling $car->$speed

Calling $car->$speed assumes that you call $car->speed because $speed defined as 'speed'.

It's PHP part of the code.

Or you can simply call $car->speed if you need to access the 'speed' property of $car object

edited Sep 13, 2011 at 8:01

answered Sep 13, 2011 at 7:30

s.webbandit

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5 Comments

sunset Over a year ago

how to define speed variable? Please give me an example based on what i wrote

sunset Over a year ago

where to add this?in vehicles.cc? can you please be more specific? i am new to php

sunset Over a year ago

i did use $car->speed but it's not working. i have the error: Undefined property: Car::$speed

s.webbandit Over a year ago

I think you should define public 'speed' property in your C++ class. And then access it by $car->speed

sunset Over a year ago

int speed is public. or what do you mean?

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