PHP - Boolen Expression Tester

<?php
 class Boolean_Tester {
    private $expression;
    private $vars;
    private $num_vars;
    private $temp_array;
    function __construct($e) {
       $e=str_replace(array(" AND "," OR "),array("&&","||"),$e);
       $this->expression=$e;
       preg_match_all('/\$?\w[\w\d]*/',$e,$matches);
       $this->vars=array();
       foreach ($matches[0] as $match) {
          if (!preg_match("/^(true|false)$/i",$match)) {
             $this->vars[$match]=true;
          }
       }
       $pos=0;
       foreach ($this->vars as $var => $nothing) {
          $this->vars[$pos++]=$var;
          unset($this->vars[$var]);
       }
       $this->num_vars=count($this->vars);
    }
    function test() {
       $argv=func_get_args();
       $count=count($argv);
       if ($count>0&&is_array($argv[0])) {
          $argv=$argv[0];
          $count=count($argv);
       }
       if ($count!=$this->num_vars) {
          trigger_error("Boolean test arguments must match",E_USER_WARNING);
          return;
       }
       foreach ($argv as &$arg) {
          $arg=$arg=="T"?"true":($arg=="F"?"false":(int)$arg);
       }
       $e=str_replace($this->vars,$argv,$this->expression);
       return eval("return $e;");
    }
    function multi_test() {
       $argv=func_get_args();
       $count=count($argv);
       if ($count==0) {
          $this->temp_array=array();
       } elseif (is_array($argv[0])) {
          if (isset($argv[1])) {
             $argv[0][]=$argv[1];
             $argv=$argv[0];
          }
          $count=count($argv);
       }
       if ($count<$this->num_vars) {
          $this->multi_test($argv,"T");
          $this->multi_test($argv,"F");
       } else {
          $this->temp_array[implode("|",$argv)]=$this->test($argv)?"T":"F";
       }
       if ($count==0) {
          $strs=array();
          $sep="+";
          $header="|";
          $sps=array();
          foreach ($this->vars as $index => $var) {
             $len=strlen($var);
             $header.=" $var |";
             $sep.="-".str_repeat("-",$len)."-+";
             $sps[$index]=str_repeat(" ",$len-1);
          }
          $header.=" Result |";
          $sep.="--------+";
          foreach ($this->temp_array as $index => $temp) {
             $str="|";
             foreach (explode("|",$index) as $index => $bool) {
                $str.=" $bool{$sps[$index]} |";
             }
             $str.=" $temp      |";
             $strs[]=$str;
          }
          $str="Testing '{$this->expression}':\n$sep\n$header\n$sep\n".implode("\n",$strs)."\n$sep";
          return array("display"=>$str,"values"=>$this->temp_array);;
       }
    }
 }
?>

<?php
 header("Content-type: text/plain");
 $test=new Boolean_Tester('$a&&$b||$c');
 echo "Tested against TRUE, FALSE, TRUE: ".$test->test(true,false,true)."\n";
 $res=$test->multi_test();
 echo $res["display"];
?>

Tested against TRUE, FALSE, TRUE: 1
Testing '$a&&$b||$c':
+----+----+----+--------+
| $a | $b | $c | Result |
+----+----+----+--------+
| T  | T  | T  | T      |
| T  | T  | F  | T      |
| T  | F  | T  | T      |
| T  | F  | F  | F      |
| F  | T  | T  | T      |
| F  | T  | F  | F      |
| F  | F  | T  | T      |
| F  | F  | F  | F      |
+----+----+----+--------+