C++ popen to run PHP - php

Question

i'm using popenRWE from http://www.jukie.net/bart/blog/popenRWE and making the script below
int pipes[3];
int pid;
const char *const args[] = {
"php ",
NULL
};
pid = popenRWE(pipes, args[0], args);
char *cmd = "<?php echo 'hello world';?> ";
cout << "write: " << write(pipes[0], cmd, strlen(cmd)) << endl;
cout << "err: " << errno << endl;
char res[100];
cout << "read: " << read(pipes[1], res, 100) << endl;
cout << "result: " << res << endl;
when i use cat command, it works, the input is the ouput (that's what cat doing), but using php the read is empty. i have confirmed that php is installed and on my path by running
echo "<?php echo 'hello world';?>" | php
directly on the console, and got the output. Can someone please advise or help on this code? Thanks in advance.

Answer 1

There are three problems with your code:
There is no executable named "php ". There is just "php" (notice that there is no space). The reason why this does not work is beceause popenRWE uses execvp which does not start a shell to execute the command but it expects the filename of the binary you want to executed (it searches for it in $PATH though).
You should close the stdin-filehandle after you've written your data, otherwise you might have to wait indefinitely for the output to be written.
Also you should wait for the php-process to finish using waitpid because otherwise you might "lose" some of the output.
To wrap it up:
int pipes[3];
int pid;
const char *const args[] = {
"php",
NULL
};
pid = popenRWE(pipes, args[0], args);
char *cmd = "<?php echo 'hello world', \"\\n\";?> ";
cout << "write: " << write(pipes[0], cmd, strlen(cmd)) << endl;
cout << "err: " << errno << endl;
close(pipes[0]);
// TODO: proper error handling
int status;
waitpid(pid, &status, 0);
char res[100];
int bytesRead = read(pipes[1], res, (sizeof(res)/sizeof(char))-1);
// zero terminate the string
res[bytesRead >= 0 ? bytesRead : 0] = '\0';
cout << "read: " << bytesRead << endl;
cout << "result: " << res << endl;