analytical algorithm

I wrote a parsing program in php when I had nothing to do these days.

For example: (21*12-23-(21+14-(21-31/3+(14-21*12-14))+54)-21)+21*25-22*26

Then The result of the analysis is: -169.33.

The code is now posted. If there is anything wrong, please fellow programmers point it out.

if(isset($_GET['sizhi'])){
    $sizhi=$_GET['sizhi'];
    if(!checkSizhi($sizhi)){
      echo('算式不合法,检查括号是否配对');
    }else{
     $sizhi=priority($sizhi);
     echo(calculate($sizhi)); 
    }
}
 //检查算式是否合法
function checkSizhi($sizhi){
    $Amatch=array();
    $pattern='/((\d|!)\()|([-\+\*\/]\))|[^-\+\*\/!\d\(\)]/';
    if(preg_match($pattern,$sizhi,$Amatch)>0){
      echo('不合法的元素：');
      print_r($Amatch);
      return false;
    }else{
      $kuohao=0;
      for($i=0,$k=strlen($sizhi);$i<$k;$i++){
         if($sizhi[$i]=="("){
               $kuohao++;
         }
         if($sizhi[$i]==")"){
               $kuohao--;
               if($kuohao<0)return false;
         }
      }
      if($kuohao!=0)return false;
      return true;
    }
}
//获得优先权 处理括号内的内容
function priority($sizhi,$start=0){
   for($i=$start;$i<strlen($sizhi);$i++){
     if($sizhi[$i]=="("){
      //递归深内层括号
      $sizhi=priority($sizhi,$i+1);
     }
     if($sizhi[$i]==")"){
       $str=calculate(trim(substr($sizhi,$start-1,$i-$start+2),"\(\)")); 
       //用计算结果替换括号内的东西
       $sizhi=substr_replace($sizhi,$str,$start-1,$i-$start+2);
       //返回内层替换后的字符串
       return $sizhi;
     } 
   }
   return $sizhi;
}
  //计算结果
function calculate($sizhi){
  //在算式前加上+ 号 以便后面用正则提取
  if($sizhi[0]!="-"){
    $sizhi=&#39;+&#39;.$sizhi;
  }
  //处理阶乘
  //判断阶乘是否合法  因为3的双重阶乘就就已经很大了
  $erropar=&#39;/(\.[0-9]+!+)|!{3,}/&#39;;
  $par=&#39;/[1-9][0-9]*!{1,2}/&#39;;
  if(preg_match($erropar, $sizhi)>0){
     echo("阶乘阶段出问题，请改算式");
     exit();
  }else{
    //替换所有阶乘的部分
   $sizhi=preg_replace_callback($par,function($siz){
          return calculateFactorial($siz[0]);
    } 
      , $sizhi);
  }
  //交换符号与数字并计算  
  return change($sizhi);
}
//计算阶乘
function calculateFactorial($sizhi){
      for ($i=0; $i <strlen($sizhi); $i++) { 
         if($sizhi[$i]==&#39;!&#39;){
            $number=substr($sizhi,0,$i)*1;
            $product=1;
            for($j=1;$j<=$number;$j++){
                 $product*=$j;
            }
            $sizhi=substr_replace($sizhi,$product,0,$i+1);
            //递归处理多重阶乘
            return calculateFactorial($sizhi);
         }
      }
      return $sizhi;
}
function change($sizhi){
    if($sizhi[0]!="-"){
       $sizhi=&#39;+&#39;.$sizhi;
    }
    $array=array();
    //提取单个算式 并保存到数组中 提取结果为：例如 +5-3*8/5 提取结果为：+5 -3 *8 /5
    $par=&#39;/[-\+\/\*]-?(\d\.?)+/&#39;;
    preg_match_all($par, $sizhi, $array);
    return sum($array[0]);
}
//计算只含加减乘除的算式
function sum($ziArry){
   for($i=0;$i<count($ziArry);$i++){
    //先计算乘除 遍历整个算式数组 如果有一个数组前边的符号为乘号或者除号 则与前数想乘除 
    //并把前一个清空，然后清除数组中空的元素
       if($ziArry[$i][0]=="*"||$ziArry[$i][0]=="/"){
           $ziArry[$i]=$ziArry[$i-1][0].calut(substr($ziArry[$i-1],1),substr($ziArry[$i],1),$ziArry[$i][0]);
            $ziArry[$i-1]="";
       }    
    }
    //清除数组中空的元素
   $ziArry=calerNu($ziArry);
   //计算加减
    for($i=0;$i<count($ziArry);$i++){
        if($i==0&&$ziArry[0][0]=="-"){
            $ziArry[1]=&#39;+&#39;.calut($ziArry[0],substr($ziArry[1],1),$ziArry[1][0]);
            $ziArry[0]="+0";
        }else if($i!=0){
         $ziArry[$i]=$ziArry[$i-1][0].calut(substr($ziArry[$i-1],1),substr($ziArry[$i],1),$ziArry[$i][0]);
         $ziArry[$i-1]=""; 
        }      
    }
    //去符号
   $relus=calerNu($ziArry)[0];
   if(($relus[0]==$relus[1]&&$relus[0]==&#39;-&#39;)||($relus[0]==$relus[1]&&$relus[0]==&#39;+&#39;)){
     return substr($relus,2);
   }
   if(($relus[0]==&#39;+&#39;&&$relus[0]==&#39;-&#39;)||($relus[0]==&#39;-&#39;&&$relus[0]==&#39;+&#39;)){
    return &#39;-&#39;.substr($relus,2);
   }
    return substr($relus,1);
}
//清除数组中的空元素
function calerNu($array){
   for($i=0;$i<count($array);$i++){
      if($array[$i]==""){
        for ($k=$i; $k<count($array)-1; $k++) { 
             $array[$k]=$array[$k+1];
          } 
          $last=array_pop($array); 
          return calerNu($array);
      }
   }
   return $array;
}
function calut($numberone,$numbertwo,$fu){
    $number
    $numbertwo=$numbertwo*1;
    switch ($fu) {
      case &#39;-&#39;:
         return $numberone-$numbertwo;
      case &#39;+&#39;:
         return $numberone+$numbertwo;
      case &#39;*&#39;:
        return $numberone*$numbertwo;
      case &#39;/&#39;:
          $str=(string)$numberone/$numbertwo;
          //如果除不尽则保留小数点后两位
          $par=&#39;/-?\d+\.\d{2}/&#39;;
          $array=array();
          if(preg_match($par, $str,$array)>0){
            $str=$array[0];
           }
         return $str;
    }
}

The above has introduced the analysis algorithm of the calculation formula, including the relevant aspects. I hope it will be helpful to friends who are interested in PHP tutorials.