How can you check if an external program is currently running in PHP?

To check if an external program is currently running in PHP, you can use the `exec()` function to execute a command that checks for the process. You can use a command like `ps aux | grep <program_name>` to search for the process by its name. If the command returns any output, then the program is running.

$programName = "my_program";
$output = shell_exec("ps aux | grep $programName");

if (strpos($output, $programName) !== false) {
    echo "The program $programName is currently running.";
} else {
    echo "The program $programName is not running.";
}