How to get executable

Assuming you're using Linux, you can use:

function getBinaryRunner($binary)
{
    return trim(shell_exec('which '.$binary));
}

For instance, same may be used for checking if needed stuff is installed:

function checkIfCommandExists($command)
{
    $result = shell_exec('which '.$command);
    return !empty($result);
}

Some points:

• Yes, it will work only for Linux
• You should be careful with user input if it is allowed to be passed to shell commands: escapeshellarg() and company
• Indeed, normally PHP should not be used for stuff like this as if it is about asynchronous requests, better to either implement forking or run commands from external workers.

How to pass parameters

With doing shell_exec() via file system path you're accessing the file and, obviously, all "GET" parameters are becoming just part of file name, it is no longer "URI" as there is no web-server to process that. So you have two options:

• Invoke call via accessing your web-server. So it will be like:

  //Yes, you will use wget or, better, curl to make web-request from CLI
  shell_exec('wget http://your.web-server.domain/script.php?foo=bar');
  

  Downside here: if you'll access your web-server via public DNS, it will cause network gap and all processing overheads. Benefit - obviously, you will not have to expect anything else in your script and make no distinction between CLI and non-CLI calls

• Use $_SERVER array in your script and pass parameters as it should be with CLI:

  shell_exec('/usr/bin/php /path/to/script.php foo bar');
  
  //inside your script.php you will see:
  //$_SERVER['argv'][0] is "script.php"
  //$_SERVER['argv'][1] is "foo"
  //$_SERVER['argv'][2] is "bar"
  

  Yes, it will require modification in the script, and, probably, some logic of how to map "regular" web-requests and CLI ones. I would suggest even to think of separating CLI-related stuff to different scripts bundle so not to mess that logic.

More about "asynchronous run"

When you do php script.php & you just run it in background mode. That, however, still keeps parent-child relation for your process. That means - if parent process dies, it's childs will also be removed. To be precise, SIGHUP will be triggered and to avoid this situation you should use nohup command. It will allow to emulate "detaching" of a process and therefore making it's run reliable and independent of circumstances happening to parent process.