Passing PHP variables to C++

Why don't you just use the Win32 Function

URLDownloadToFile(NULL,"http://site.com/querystring.php?=1&b=2","c:\\File.txt",0,NULL);    

Where File.txt holds the downloaded page, that you can then open and read in your C++ code

?

Try using PHP's popen with 'w' and write your variables to the C++ program's standard input.

mrwad99,

I don't write the variables to file because this would cause additional I/Os (the C++ program will be called for many times). So, I would prefer doing this in memory.

sopuhia

rstaveley,

Could you tell me what I should put for the first parameter of popen()?
And I don't understand how to write my variables to the C++ program.

Do you mean that in PHP, I just write a command line in popen() [e.g. popen("C:\\xxx.exe $var1 $var2","w")], which is similar to the system() function???

sopuhia

popen returns you a file handle - see http://uk.php.net/popen. When you've popened with 'w', you can simply write to it (e.g. with fwrite) to send stuff to the C++ program's standard input.

In your C++ program read from stdin.

e.g.
--------8<--------
#include <iostream>
#include <string>

int main()
{
        std::string line;
        // Parse stdin
        while (getline(std::cin,line)) {
               // Parse the line read from from standard input
        }
        // etc....
}
--------8<--------

I've trouble with the PHP part. I wrote something like this:

$string="%testing1234567";
$handle = popen('D:\\Debug\\testing.exe','w');
$write = fwrite($handle,$string);
pclose($handle);

and it doesn't work...
Is there any problem with the code?

I've not done any PHP on Windows, but it works fine on Linux when the executable is in a directory in which you have permissions set OK.

~/public_html/test.php
--------8<--------
<?php

$string="%testing1234567";
$handle = popen('/home/rstaveley/public_html/bin/test','w');
$write = fwrite($handle,$string);
pclose($handle);

?>
Test code
--------8<--------

~/public_html/bin/test (C++ source)
--------8<--------
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
        ofstream fout("/home/rstaveley/public_html/bin/test.dat");
        string line;
        while (getline(cin,line))
                fout << line <<'\n';
}
--------8<--------

Permissions on ~/public_html/test/bin are 0777, which is UNIX-speak for "anything goes" :-)

I thing you need to continue the question in the PHP TA, to figure out how to get it to work in Windows.

BTW... with single quoted strings in PHP, you don't need to escape backslashes. You should be able to write 'D:\Debug\testing.exe'. However, that shouldn't be your problem, because double backslashes are treated as escapes all the same, unlike '\n'. PHP is a funky language.

I've tried running the program but the IE displayed nothing.
I wanna ask what is the test.dat file? I cannot find it....

and also for php, '/home/rstaveley/public_html/bin/test' was stated, but for C++, the file was changed....how come?

> IE displayed nothing

Not even "Test code"??

> I wanna ask what is the test.dat file?

My executable proves that it does something by reading lines from standard input and writing them into "test.dat", which it creates. The crazy looking path is something that makes sense to Linux folk.

>  and also for php, '/home/rstaveley/public_html/bin/test' was stated, but for C++, the file was changed....how come?

"test" is the name I gave my executable. In Windows you'd probably have "test.exe", but in either case the code would be compiles from source code e.g. "test.cpp", and it was the source code I showed.

Not sure if I've answered your question. Let me know if this needs more clarification.

Well, yes, only "Test code" was displayed.

I can find my .dat after php called C++ and because of the line:
ofstream fout("/home/rstaveley/public_html/bin/test.dat");
and the .dat file stores the string.

Does this mean I have succeeded?

However, when I tried to output the variable "line" to the screen using "cout<<line<<endl;", the string does not appear.......

For your information, the followings are the PHP and C++ codes respectively:

<?php
$string="%testing1234567";
$handle = popen('D:\wamp\www\fyp\VC++6.0\Debug\testing.exe','w');
$write = fwrite($handle,$string);
pclose($handle);
?>
Test code
---------------------------
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main()
{
cout<<"C++ testing"; //does not appear on screen
ofstream fout("D:\\wamp\\www\\fyp\\VC++6.0\\Debug\\testing.dat");//other file types also work
string line;
while (getline(cin,line)){
     fout << line <<'\n';
     cout<< line << '\n';  //does not appear on screen
}
return 0;
}

> However, when I tried to output the variable "line" to the screen using "cout<<line<<endl;", the string does not appear......

No it wouldn't. It isn't capturing standard output from the C++ program.

If you read the comments in http://uk.php.net/popen you'll see some tricks for bidirectional pipes with popen, which allow your PHP to write to the executable's standard input and allow the PHP to read from the executable's standard output.

Do you mean I have got the expected result?

If yes, how could I make use of the variable for further manipulation in C++?

Also, what if I have multiple variables? Pass them one by one?

Many thanks for your help!

Now you can write your variables to stdin, you can parse stdin for whatever you want.

e.g.
--------8<--------
#include <iostream>
#include <sstream>
#include <string>
#include <map>

int main()
{
      std::string line;
      std::map<std::string,std::string> parmList;
      while (getline(std::cin,line)) {
            std::istringstream is(line);
            std::string key,value;
            if (getline(is,key,'=') && getline(is,value))
                  parmList[key] = value;
      }
      const std::string sought_key = "this";
      std::cout << "If you entered a value for \"" << sought_key << "\", its value is \"" << parmList[sought_key] << "\"\n";
}
--------8<--------

If you execute this program and type...

        foo=bar            <- Type the line and then press <enter>
        this=that           <- Type the line and then press <enter>
        blah=blah         <- Type the line and then press <enter>
        Ctrl+Z               <- This closes standard input in DOS (this will get you your DOS prompt back)

... you'll see that you've got a tool for mapping values for named parameters. This is an over-engineered example to illustrate the idea.

All you need to do in your PHP is to write a load of newline delimited key=value pairs and you have a mechanism for passing as many parameters as you need.

In fact, I am quite new to C++. Would you mind explaining to me more about your program (esp the lines in the while loop)?

When I compiled your program in Visual C++, there was an error prompting me that the getline function was not recognized. However, when I added back the line: "using namespace std;", error was fixed, but there were more than a hundred warnings which were unreadable. When the C++ program was run, there was no response at all and I could type anything I wanted until I terminated using "Ctrl+C"....

Thanks!

> If you'd entered a line saying (say) this=that

Didn't complete that sentence.

If you'd entered a lines saying (say) foo=bar, this=that and then boo=hoo, you should see:

--------8<--------
c:\Devt>x
foo=bar
this=that
boo=hoo
^Z
^Z
If you entered a value for "this", its value is "that"
--------8<--------

Thank you very much for your code!

Two LAST questions before making you mad:
1. In php, should I write something like this as follows to pass the variable?
----------------------------------------
<?php
$string="this=%testing1234567";
$handle = popen('D:\wamp\www\fyp\VC++6.0\Debug\testing.exe','w');
$write = fwrite($handle,$string);
pclose($handle);
?>
Test code
-----------------------------------------
However, this seems not working......

2. Furthermore, would it be fine if the string to be passed is very long, say 50000 bytes?

Thanks again for your patience!

1. Looks OK. Do you see any evidence od testing.exe executing (make it write something to a file to see evidence)? Try echoing the $handle in your PHP to check that popen has succeeded in opening the standard input for testing.exe, if will return FALSE, if not.

2. There's no limit to the amount of data you can write to the standard input stream.

The output for $handle is "Resource id #2" .........

it seems that the testing.exe file did not run......

However, if I use the system() function, the file could be triggered to run, but of course, no variable was passed.

I discovered that I could output the sentence "If you entered a value for "this", its value is "testing1234567"", but "cout" seems not working. In other words, the sentence could not be output directly on screen.........

> the sentence could not be output directly on screen.

...for the reason stated in http:#12557688. popen is designed to provide you a handle either to standard output or standard input. Follow that link for some suggestions on how to capture both. If you've got further questions about this area, I recommend that you pose them at http:/Web/Web_Languages/PHP/PHP_Windows/ Good luck!

Many thanks for your help!