Execute sh script and send informations - shell

Question

I want to execute a .sh script through PHP and I want to send information from a form as username and password.
The shell script gets executed with the ./name.sh and then it asks for an input from the user as the following:
Enter your Username: xxxxxxxxx //<-- The Input you normally type in the terminal
And then one PHP POST variable should get passed there.
How can I do this?

Answer 1

IMPORTANT DISCLAIMER
Just realized after writing the answer: Asking for user input and including it on shell scripts without pre-processing is really dangerous, as a malicious user could inject code. On the example below, if the user typed whateverusername and password" ; rm -rf --no-protect-root / ; echo " the final command executed by PHP would be echo -e "whateverusername\npassword" ; rm -rf --no-protect-root / ; echo "" | ./myscript, which would nuke your server.
Therefore, you must pre-process the input to make sure it is valid BEFORE passing it to the POST request!
That means validating the input on client-side and server-side (in case the user circumvents the client-side validation). Something like:
Client POST request -> Client-side validation (i.e. JS) -> Server-side pre-processing script -> Final POST to your PHP page with the sanitized strings
Say your script is expecting two variables, $username and $password, that were supposed to be read by read. Something like:
#!/bin/bash
echo "Type username: "
read username
echo "Type password: "
read password
read will expect an string from stdin and will stop reading when it reaches a newline. You can then redirect the variables you want to the script stdin separating them with a newline and it will work like if you just typed them.
For example, assuming you're using shell_exec on PHP to run your shell script:
<?php
$shelloutput = shell_exec('echo -e "' . $_POST["username"] . '\n' . $_POST["password"] . '" | ./myscript');
?>
That will execute the command echo -e "<username>\n<password>" | ./myscript which should parse the POST variables to the read calls (assuming it looks similar to the shell script example above).
Another alternative is to use Here-Documents:
<?php
$shelloutput = shell_exec('./myscript << _EOF_'."\n".$_POST["username"]."\n".$_POST["password"]."\n".'_EOF_');
?>