How to write to the outgoing for the parent (incoming for the child) stream in ProcessBildere in java?

Question

Java

jaba

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintWriter;

public class test {
    public static void main(String args[]) throws Exception {
        Process pb = new ProcessBuilder().command("php", "php.php", "123").start();
        BufferedReader in = new BufferedReader(new InputStreamReader(pb.getInputStream()));
        PrintWriter out = new PrintWriter(pb.getOutputStream());

        Thread.sleep(1000);
        out.println("321\r\n\r\n");

        System.out.println(in.readLine());
        System.out.println(in.readLine());
        System.out.println(in.readLine());
        System.out.println(in.readLine());
        System.out.println(in.readLine());

    }
}

----------------
pha

<?

$f = fopen("php://stdin","r+");
$read = fread($f,4096);
$read = str_replace("\r\n","",$read);
fclose($f);

echo "3331\n";
echo $argv[1]."\n";
echo "3332\n";
echo $read."\n";
echo "3333\n";

Output:
null
null
null
null
null
null

Expected output:
3331
123
3332
321
3333

Why does the program output incorrect values?