Closes a file pointer to a pipe opened by popen.
The file pointer must be valid, and must have been returned by a successful call to popen.
Returns the termination status of the process that was run. In case of an error then -1 is returned.
If PHP has been compiled with --enable-sigchild, the return value of this function is undefined.
pclose is internally implemented using the waitpid(3) system call. To obtain the real exit status code the pcntl_wexitstatus function should be used.