<?php
/**
 * math_rpn 
 *
 * 實(shí)現(xiàn)逆波蘭式算法
 *  
 */
class math_rpn {
  //初始的計(jì)算表達(dá)式
  private $_expression = '';
  //處理后的逆波蘭表達(dá)式
  private $_rpnexp = array();
  //模擬棧結(jié)構(gòu)的數(shù)組
  private $_stack = array('#');
  //正則判斷
  //private $_reg  = '/^([A-Za-z0-9\(\)\+\-\*\/])*$/';
  //優(yōu)先級(jí)
  private $_priority = array('#' => 0, '(' => 10, '+' => 20, '-' => 20, '*' => 30, '/' => 30);
  //四則運(yùn)算
  private $_operator = array('(', '+', '-', '*', '/', ')');
  public function __construct($expression) {
    $this->_init($expression);
  }
  private function _init($expression) {
    $this->_expression = $expression;
  }
  public function exp2rpn() {
    $len = strlen($this->_expression);
    for($i = 0; $i < $len; $i++) {
      $char = substr($this->_expression, $i, 1);
      if ($char == '(') {
        $this->_stack[] = $char;
        continue;
      } else if ( ! in_array($char, $this->_operator)) {
        $this->_rpnexp[] = $char;
        continue;
      } else if ($char == ')') {
        for($j = count($this->_stack); $j >= 0; $j--) {
          $tmp = array_pop($this->_stack);
          if ($tmp == "(") {
            break; 
          } else {
            $this->_rpnexp[] = $tmp;
          }
        }
        continue;
      } else if ($this->_priority[$char] <= $this->_priority[end($this->_stack)]) {
        $this->_rpnexp[] = array_pop($this->_stack);
        $this->_stack[] = $char;
        continue;
      } else {
        $this->_stack[] = $char;
        continue;
      }
    }
    for($i = count($this->_stack); $i >= 0; $i--) {
      if (end($this->_stack) == '#') break;
      $this->_rpnexp[] = array_pop($this->_stack); 
    }
    return $this->_rpnexp;
  }
}
//測(cè)試實(shí)例
$expression = "(A*(B+C)-E+F)*G";
var_dump($expression);
$mathrpn = new math_rpn($expression);
var_dump($mathrpn->exp2rpn());
/*End of php*/