<?php
    $weapons = ['fists', 'whip', 'gun'];
    $opponentWeapon = $weapons[rand(0,2)];

    switch($opponentWeapon) {
        case $weapons[0] :
            echo $indyWeapon = $weapons[2];
            break;

        case $weapons[1] :
            echo $indyWeapon = $weapons[0];
            break;

        case $weapons[2] :
            echo $indyWeapon = $weapons[1];
            break;
    }
    echo $opponentWeapon; //For Test