Multiple input with proc_open()

Question

I'm currently working on an online program. I'm writing a php script that executes a command in the command line with proc_open() (under Linux Ubuntu). This is my code so far:

<?php
$cmd = "./power";

$descriptorspec = array(
   0 => array("pipe", "r"),
   1 => array("pipe", "w"),
   2 => array("pipe", "w"),
);

$process = proc_open($cmd, $descriptorspec, $pipes);

if (is_resource($process)) {

    fwrite($pipes[0], "4");
    fwrite($pipes[0], "5");
    fclose($pipes[0]);

    while($pdf_content = fgets($pipes[1]))
    {
        echo $pdf_content . "<br>";
    }
    fclose($pipes[1]);

    $return_value = proc_close($process);
}
?>

power is a program that asks for input 2 times (it takes a base and an exponent and calculates base ^ exponent). It's written in Assembly. But when I run this script, I get wrong output. My output is "1" but I expect 4^5 as output.

When I Run a program that takes one input, it works (I've tested an easy program that increments the entered value by one).

I think I'm missing something regarding the fwrite command. Could anyone please help me?

Thanks in advance!

Answer 1

You forgot to write a newline to the pipe, so your program will think that it got only 45 as input. Try this:

fwrite($pipes[0], "4");
fwrite($pipes[0], "\n");
fwrite($pipes[0], "5");
fclose($pipes[0]);

Or shorter:

fwrite($pipes[0], "4\n5");
fclose($pipes[0]);