1. Introduction

If you know something about Unix/Linux, you should know that most of them come with C and C++ compilers, namely GCC and G++ respectively. Unix uses these compilers in many places such as program installation and Make. Using some console commands, C++ and PHP, I will show you how to generate a complete C++ program example that can be executed in a PHP program and get the corresponding output results. I will first generate the C++ program code, compile it, and then discuss how we will execute this program by using the PHP function passthru. In a sense, this article provides us with a way to access general programs through Web pages.

In order to better understand this article, you should have a Unix/Linux server running Apache and the latest version of PHP. At the same time, you should also master C++ and unix console commands. Of course, some PHP programming experience is also required.

2. Write a C++ program

For example, we can write a simple C++ program that can also receive parameters through the command line, and name it Sampleapp. Then we can pass it three different parameters in the following way:

Sampleapp – parameter one – parameter two – parameter three

The function of this program is to output the number of parameters passed to it and the value of each parameter. Then we can use a PHP script program to execute the compiled C++ program.

Use your favorite text editor to create a new file named Sampleapp.cpp, and enter the following code into this file:

#include

int main(int argc, char* argv[])
{
cout << endl << "You passed " << argc-1 << " argumentment"
<< (argc-1 == 1 ? "" : "s") << "." << endl;

cout << (argc-1 == 1 ? "This" : "These")
<< " argument" << (argc-1 == 1 ? "" : "s") << " "
<< (argc-1 == 1 ? "is" : "are") << ": " << endl << endl;

for(int i = 1; i < argc; i++)
cout << "[" << i << "] " << argv[i] << endl;

return 0;
}

This C++ program contains the entry point of the program: main(). The main() function takes two parameters: argc (the number of parameters passed in from the command line) and argv (a character pointer containing the actual value of the passed parameter). array). These two parameters can be automatically captured by the C++ compiler.

cout << endl << "You passed " << argc-1 << " argumentment"
<< (argc-1 == 1 ? "" : "s") << "." << endl;;

This sentence means to get the number of parameters passed in from the execution command line. The character pointer array Argv is retrieved starting from 0. It contains at least one actual value (that is, the path and name of this program). This value is automatically appended by the C++ compiler. The conditional operator "?" is used to determine whether there is more than one parameter passed in from the command line. For example, if two parameters are passed in from the command line, our program will output the following information:

You passed 2 arguments.

cout << (argc-1 == 1 ? "This" : "These")
<< " argument" << (argc-1 == 1 ? "" : "s") << " "
<< (argc-1 == 1 ? "is" : "are") << ": " << endl << endl;

Next, we also use conditional operators to output another sentence. But remember, even if we don't pass in any parameters from the program execution command line, the argv[] parameter of the main function contains a value. Similarly, if we pass two parameters to the program from the command line, the program will output the following information:

These arguments are:

for(int i = 1; i < argc; i++)
cout << "[" << i << "] " << argv[i] << endl;

Finally, the main function outputs each parameter passed in from the command line one by one. It uses a simple for(;;) loop statement. This function can output the parameter values one by one according to the number of parameters. If we pass two parameters "first" and second" to the program, the result output by the for loop is as follows:

[1] –first
[2] –second

The above is a brief description of this C++ program. Its function is very simple, which is to display the parameters passed in from the command line on the output screen using the cout function.

Next, we will compile this .cpp file. If you are on the Windows platform, you need to telnet to the server you are using. Here, we use the G++ compiler provided on most Unix machines to compile this source file. But to make sure that your machine has G++ installed, you can enter the following command: which g++. If G++ is already installed, the Unix shell will display the full path to where G++ is located. If it is not installed, it will prompt you saying “command couldn’t be found”. You can download G++ here.

Enter the following G++ command in the directory where the source file is located:

g++ -c sampleapp.cpp.

With this command, we compile the .cpp file into a target file containing machine code. Through the ls –a command, you can find that a new file sampleapp.o appears in this directory. This is the result of the .cpp source file being compiled into machine code. But what we ultimately want is an executable file, because we also need to enter the following G++ command:

g++ sampleapp.cpp –o sampleapp

In this way we obtain an executable file named sampleapp. However, please note that the executable file under Unix is different from Windows, it does not have any suffix.

Next we can check the results of program execution, if the command is as follows:

sampleapp one -two /three

We can see the following execution results:

You passed 3 arguments.
These arguments are:

[1] one
[2] –two
[3] /three

Now that the executable C++ program has been generated, we will generate a PHP tutorial program that can access this program through a web browser.

3. Generate PHP script program

In order to call our C++ program through the Internet, we need to generate a PHP script program. This PHP script will have a Form so that the user can enter parameters that can be passed to the Sampleapp program. The code of the PHP script is too long so I won’t list it all here. If necessary, you can download it from the address below. (Php code)

if(@$submit)
{

}
else
{
}

First, the script program checks to see if the variable $submit has a value. The value of this variable $submit is passed after the Form form is submitted later in the program. It defaults to a null value. The function of the @ symbol is to ignore the relevant error message when the value of the variable $submit does not exist.

Since the variable $submit is empty by default, the code in else{} is initially executed, which simply displays a Form on the browser. The action attribute of the Form is set to the variable $PHP_SELF, that is, this page is returned after the form is submitted. At the same time, the Form form contains a text input bar, which is used to allow users to enter command line parameters to be passed to the C++ program. Form is as shown below:

Once we enter the execution command and submit the form, the variable $submit (the name of the button Go) gets a value, so that the PHP textbook will execute the code between if{}.

if($args == "")
echo "

You didnt enter any arguments.

";
else
{
echo "

SampleApp Result

";
$command = "/htdocs/sampleapp " . escapeshellcmd($args);

passthru($command);
}

The variable $args is automatically generated, and its value is the value passed from the text input bar in the Form form. If no information is entered, the program will simply tell the user that no value was entered.

If the user enters any non-empty information, the program will pass the value of the text field, the variable $args, to the C++ program. The following code is the execution command for executing a C++ program:

$command = "/htdocs/sampleapp " . escapeshellcmd($args);

The function ecapeshellcmd is used as a security check tool to filter out special characters such as ",", "" and "". This prevents some users from trying to enter certain characters to invoke internal system commands.

For example, if you enter "1 –two /three" in the text field of the Form form, then the value of the variable $command is: /htdocs/sampleapp 1 –two /three

You can see that we defined the full path of the program sampleapp. In this example, the program file is located in the /htdocs directory. You can make corresponding modifications according to the directory where your own program is located.

passthru($command);

Finally, we use the PHP function passthru to execute the command contained in the variable $command and output the original execution results to the browser. On my server, the HTML page that returns the results is as follows:

wBefore the end of this article, I would like to talk about a few problems that may be encountered. First of all, when you execute the sampleapp.php tutorial program, if you do not see any output information from the program, it may be that the safe mode is turned on. If so, the system will not allow PHP scripts to execute system internal programs. Regarding how to turn off safe mode, please visit the web page http://www.php.net/manual/en/features.safe-mode.php, which has detailed introduction. Secondly, on some Unix systems, the PHP function passthru cannot pass the output of the internal program to the browsing page, if this happens

Using PHP to execute C/C++ programs through the Web_PHP Tutorial

You didnt enter any arguments.

SampleApp Result