php run another script in foreground - php

Question

I have a php script that leads up to running another expect script by passing it arguments.
$output = shell_exec("expect login_script.tcl '$user' '$host' '$port' '$password'");
Using shell_exec doesn't work as the script gets run in the background or 'within' the php script. I need it to run in the foreground, allowing user interactivity. Is there an elegant way to do this. Already it is getting messy by having to use different scripting languages. I tried wrapping the two scripts with a shell script that called the php script, assigned output the result as a variable (which was a command) and then ran sh on that. However I have the same problem again where the scripts are run in the background and any user interactivity creates a halt/freeze. Its ok in this situation if php 'quits' out when calling shell exec. Ie. php stops and expect gets run as if you called it. (the same as if i just copied the command that is output and pasted it into the terminal).
Update
I am having much more luck with the following command in php:
shell_exec("gnome-terminal -e 'bash -c \"expect ~/commands/login_script.tcl; exec bash\"' &");
However, can this be improved in order to not close the shell immediately after the secondary script (login_script) is finished?
Further Update
From reading the answers I think I need to clarify things as it looks like people are assuming a 'more complicated' issue.
the two processes do not need to communicate with each other, I should probably not have put the $output = shell_exec in the example and just shell_exec on its own as I believe this has led to the confusion.
The php script needs to only initiate the expect script with some cli parameters, e.g. my-script 'param1' 'param2' and can be thought of as completely 'asynchronous'. This is much like the behaviour of launcher programs like 'launchy' or 'synapse' they can launch other programs but need not affect them. Nor do they wait for the secondary program to quit/finish.
I made the mistake of saying 'shell_exec' doesn't work for me. What I should have said was that 'I have so far not succeeded with using shell_exec', but shell_exec("gnome-terminal -e 'bash -c \"expect ~/commands/login_script.tcl; exec bash\"' &"); is 'working' but still trying to find the right quote combination to allow passing arguments to the expect script.

Answer 1

Task managing is an interesting but difficult job.
Because your user can move during a task (and leads it to an unexpected result, such as session freezes, or an incomplete work from the process), you need to execute it in background. If you need to interact between your user and your process, you'll need to create a way to communicate.
The easiest way (I think) is to use a file, shared between your user session and the task.
If you have a lot of users simultaneously and communicates a lot between user and processes, you can mount a partition in memory to optimize the read/write operations.
In your fstab, a line like :
tmpfs /memory tmpfs defaults,uid=www-data,gid=www-data,size=128M 0 0
Or, in a script, you could do :
#!/bin/sh
mkfs -t ext2 -q /dev/ram1 65536
[ ! -d /memory ] && mkdir -p /memory
mount /dev/ram1 /memory
chmod -R 777 /memory
You'll need to take care of a lot of things :
file access (to avoid concurrency between your webapp and your processes)
time (to avoid zombies or useless long-running scripts)
security (such operations must be carefully designed)
resources management (to avoid that 10000 processes runs simuntaneouly)
...

Answer 2

I think what you're looking for is the proc_open() command. It gives you access to the stdin/stdout streams of the background process. You can pass your own stdin/stdout streams to the new process in the $descriptorSpec parameter, which will let your background process talk to the user.
Your 'foreground' application will have to wait around until the background process has died. I haven't actuallly done this with PHP, but I'm guessing you'll have to watch the $pipes to see when they get closed -- then you'll know the background process is finished and you can delete the process resource and continue on with whatever the foreground process needs to do.

Answer 3

In the end, I managed to get it working by by adding a third quotation mark type: ` (I believe it is called a 'tack'?) which allowed me to pass arguments to the next script from the first script
The command I needed in my php script was:
$command = `gnome-terminal -e 'bash -c "expect ~/commands/login_script.tcl \"$user\" \"$host\" \"$port\" \"$password\"; exec bash"' &`;
shell_exec($command);
It took a while to get all the quotes right as swapping the type of quotes around can lead to it not working.
Here is a video demonstrating the end result

Answer 4

Use:
pcntl_exec("command", array("parameter1", "parameter2"));
For example, I have a script that starts the mysql command using the parameters in the current php project that looks like:
pcntl_exec("/usr/bin/mysql", array(
"--user=".$params['user'],
"--password=".$params['password'],
"--host=".$params['host'],
$params['dbname']
));
This doesn't rely on gnome terminal or anything, it replaces PHP with the program you call.
You do need to know the full path of the command, which is a pain because it can vary by platform, but you can use the env command command which is available at /usr/bin/env on most systems to find the command for you. The above example above becomes:
pcntl_exec("/usr/bin/env", array(
"mysql",
"--user=".$params['user'],
"--password=".$params['password'],
"--host=".$params['host'],
$params['dbname']
));