Rock, Paper, Scissors

<!-- create a form for the user's selection -->
<form action="">
  <label for="selection">Choose Rock, Paper, or Scissors:</label>
  <select name="selection" id="selection">
    <option value="Rock">Rock</option>
    <option value="Paper">Paper</option>
    <option value="Scissors">Scissors</option>
  </select>
  <input type="submit" value="Submit" />
</form>

<?php
  if (isset($_GET['selection'])) {
    // get user's selection and the computer's random selection
    $userSelection = $_GET['selection'];
    $computerSelection = rand(0, 2);

    // create an array of options
    $options = array('Rock', 'Paper', 'Scissors');

    // determine the winner
    if ($userSelection == $options[$computerSelection]) {
      echo '<h2>It's a tie!</h2>';
    } elseif (($userSelection == 'Rock' && $options[$computerSelection] == 'Scissors') || 
              ($userSelection == 'Paper' && $options[$computerSelection] == 'Rock') ||
              ($userSelection == 'Scissors' && $options[$computerSelection] == 'Paper')) {
      echo '<h2>You win!</h2>';
    } else {
      echo '<h2>You lose!</h2>';
    }
  }
?>