The script in (almost) full

As opposed to wasting space by printing such a long script several times over, I have only been printing parts so far. However, as we are done, here is the complete script, sans the gettoken() function which is unchanged:
<?php

      define("FOO_NUMBER", 0);

      define("FOO_VARIABLE", 1);

      define("FOO_ASSIGNEQUALS", 2);

      define("FOO_PRINT", 3);

      define("FOO_STRING", 4);

      define("FOO_SEMICOLON", 5);

      define("FOO_PLUS", 6);

      define("FOO_MULTIPLY", 7);

      define("IS_OPERATOR", 0);

      define("IS_OPERAND", 1);

  

      // you can change the values in $precedence, as long you keep the order the same

      $precedence = array (FOO_PRINT => 0, FOO_ASSIGNEQUALS => 1, FOO_PLUS => 2, FOO_MULTIPLY => 3);

  

      class token {

          public $type;

          public $token;

          public $val;

  

          public function __construct($type, $token, $val) {

              $this->type = $type;

              $this->token = $token;

              $this->val = $val;

          }

      }

  

      // this function converts variables to values as appropriate

      function getval($token) {

          GLOBAL $variables;

          if ($token->token == FOO_VARIABLE) {

              return $variables[$token->val];

          } else {

              return $token->val;

          }

      }

  

      function execute(&$stack) {

          GLOBAL $variables;

          $operator = array_pop($stack);

  

          if ($stack[count($stack) - 1]->type == IS_OPERATOR) {

              $right = execute($stack);

          } else {

              $right = array_pop($stack);

          }

  

          if (count($stack)) {

              if ($stack[count($stack) - 1]->type == IS_OPERATOR) {

                  $left = execute($stack);

              } else {

                  $left = array_pop($stack);

              }

          }

  

          switch($operator->token) {

              case FOO_ASSIGNEQUALS:

                  $variables[$left->val] = getval($right);

                  break;

              case FOO_PLUS:

                  return new token(IS_OPERAND, FOO_NUMBER, getval($left) + getval($right));

              case FOO_MULTIPLY:

                  return new token(IS_OPERAND, FOO_NUMBER, getval($left) * getval($right));

              case FOO_PRINT:

                  print getval($right);

                  print "\n";

          }

      }

  

      function main() {

          GLOBAL $lasttoken, $precedence;

  

          while(1) {

              $stack = array();

              $operators = array();

  

              do {

                  $token = gettoken();

  

                  switch($token) {

                      case FOO_NUMBER:

                          case FOO_VARIABLE:

                          case FOO_STRING:

                              $stack[] = new token(IS_OPERAND, $token, $lasttoken);

                              break;

                          default:

                              if ($token != FOO_SEMICOLON) {

                                  // this removes higher-precedence operators in places of a new, lower-precedence one

  

                                  while (count($operators) && $precedence[$operators[count($operators) - 1]->token] > $precedence[$token]) {

                                      $higher_op = array_pop($operators);

                                      array_push($stack, $higher_op);

                                  }

  

                                  $operators[] = new token(IS_OPERATOR, $token, NULL);

                              }

                  }

              } while ($token != FOO_SEMICOLON);

  

              while (count($operators)) array_push($stack, array_pop($operators));

  

              execute($stack);

          }

      }

  

      function gettoken() {

          // this is unchanged

      }

  

      $script = fopen("script.foo", "r");

      $characters = array_merge(range('a', 'z'), range('A', 'z'));

      $characters[] = "_";

      $variables = array();

  

      function cleanup() {

          GLOBAL $script;

          fclose($script);

      }

  

      register_shutdown_function("cleanup");

      main();
 ?>
Even with the gettoken() function all but removed, that is still probably the longest script in the entire book. Still, you like typing, right?
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