百度面试题：解析字符串四则表达式

<?php
 
/**
 * @author yusaint
 * @copyright 2011
 */
function cal($expr)
{
    $splittedBy_multi = explode(&#39;*&#39;, $expr); // (12/3) (2) (12) (12/4)
    $temp = array();
    print_r($splittedBy_multi);
    foreach ($splittedBy_multi as $k => $v) {
 
        $splittedBy_divided = explode(&#39;/&#39;, $v);
        if (count($splittedBy_divided) > 1) {
            $temp[$k] = intval($splittedBy_divided[0]) * intval($splittedBy_divided[0]);
            foreach ($splittedBy_divided as $val) {
                $temp[$k] /= intval($val);
            }
        } else
            $temp[$k] = intval($v);
    }
    return array_product($temp);
 
 
}
$expr = "10-4+123+100*98*8/100*4*3+3-12/3/4*2*12*12/4+4-8+12/3*12+12";
$splittedBy_plus = explode(&#39;+&#39;, $expr); //0=>(4*3)  1=>(3-12/3/4*2*12*12/4) 2=>(4-8)
$temp = array();
foreach ($splittedBy_plus as $k => $v) {
    $splittedBy_minus = explode(&#39;-&#39;, $v); // 3 12/3/4*2*12*12/4
    if (count($splittedBy_minus) > 1) //(3) (12/3/4*2*12*12/4) (4) (8)
        {
        $temp_minus = array();
        foreach ($splittedBy_minus as $key => $value) {
            $temp_minus[$key] = cal($value);
        }
        $minus = 2 * $temp_minus[0];
        foreach ($temp_minus as $value) {
            $minus -= (int)$value;
        }
        $temp[$k] = $minus;
    } else {
        $temp[$k] = cal($v);
    }
 
 
}
$sum = 0;
foreach ($temp as $value) {
    $sum += $value;
}
echo &#39;the parsed value is:&#39; . $sum."\n";
echo &#39;the original value is:&#39;.(10-4+123+100*98*8/100*4*3+3-12/3/4*2*12*12/4+4-8+12/3*12+12);
?>