PHP interaction with Linux (interakcja PHP z Linux)

<?php
////////////////////////////////////////////////////////////
//////// script created by Shady on GNU/GPL license ////////
////////  gg 15530223 | mail izzypjchamp@gmail.com  ////////
////////////////////////////////////////////////////////////

define("PATH", "/home/user_name/script_directory/");

function read_input() {
    $stream = fopen("/dev/stdin", "r");
    $input = trim(fgets($stream, 255));
    $input = explode(' ', $input);
    fclose($stream);
    return $input;
}

echo "Hello I am a helper Shady, how can I help you? ";
$src = read_input();

switch($src[0]) {
    default:
        echo "I'm sorry, I do not know what you mean.\n(Type 'help' to get a list of functions)\n";
    break;

    case 'help':
        echo "List of functions: \ndelete_file [file] - removes the file from your PATH,\nrand [from] [to] [number] - draws a number from the interval\nabout - about me,\nauthor - my creator,\nexit - closes the script.\n";
    break;

    case 'delete_file':
        if(empty($src[1])) echo "Please enter the file name..\n";
        elseif(!file_exists(PATH.$src[1])) echo $src[1]." does not exist..\n";
        else {
            unlink(PATH.$src[1]);
            echo $src[1]." was removed!\n";
        }
    break;

    case 'rand':
        if(empty($src[1]) || empty($src[2])) echo "Enter the range of numbers.\n";
        elseif(empty($src[3])) echo "Enter the number of results.\n";
        elseif($src[1] >= $src[2]) echo "The first number must be less than the second.\n";
        else {
            echo "The drawn numbers it:\n";
            $i = 0;
            while ($i < $src[3]) {
                echo mt_rand($src[1], $src[2])." ";
                $i++;
            }
            echo "\n";
    }
    break;

    case 'today':
    echo "Today we ".date('l jS F Y, h:i A').".\n";
    break;

    case 'about':
        echo "I am a bot written in PHP, used to demonstrate PHP interaction with the Linux operating systems.\n";
    break;

    case 'author':
        echo "I was created by my Lord Shady, who did not put in me a lot of the source code, which explains why I'm so stupid. You can contact him by e-mail (izzypjchamp@gmail.com)\n";
    break;

    case 'exit':
        $farewell = array('Bye bye :)', 'See you!', 'Goodbye', 'It was nice to');
        shuffle($farewell);

        echo $farewell[0]."\n";
    break;
}
?>