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  1. <?php
  2.  
  3. $input = "55/5*1=";
  4. $inputLength = mb_strlen($input);
  5.  
  6. $number = 0; //actual number
  7. $result = 0; //of previous actions
  8. $op = ""; //last unused operation
  9. for ($i = 0; $i < $inputLength; $i++) {
  10.     $char = mb_substr($input, $i, 1);
  11.  
  12.     if ($char == "*" || $char == "+" || $char == "-" || $char == "/") {
  13.         switch($op) {
  14.             case(""):
  15.                 $op = $char;
  16.                 $result = $number;
  17.                 $number = 0;
  18.                 break;
  19.             case ("*"):
  20.                 $result = $result * $number;
  21.                 $op = $char;
  22.                 $number = 0;
  23.                 break;
  24.             case ("+"):
  25.                 $result = $result + $number;
  26.                 $op = $char;
  27.                 $number = 0;
  28.                 break;
  29.             case ("-"):
  30.                 $result = $result - $number;
  31.                 $op = $char;
  32.                 $number = 0;
  33.                 break;
  34.             case ("/"):
  35.                 $result = $result / $number;
  36.                 $op = $char;
  37.                 $number = 0;
  38.                 break;
  39.  
  40.         }
  41.  
  42.     } elseif (is_numeric($char)) {
  43.         $number = $number * 10 + intval($char);
  44.  
  45.     } elseif ($char == "=") {
  46.         switch($op) {
  47.             case ("*"):
  48.                 $result = $result * $number;
  49.                 $op = $char;
  50.                 $number = 0;
  51.                 break;
  52.             case ("+"):
  53.                 $result = $result + $number;
  54.                 $op = $char;
  55.                 $number = 0;
  56.                 break;
  57.             case ("-"):
  58.                 $result = $result - $number;
  59.                 $op = $char;
  60.                 $number = 0;
  61.                 break;
  62.             case ("/"):
  63.                 $result = $result / $number;
  64.                 $op = $char;
  65.                 $number = 0;
  66.                 break;
  67.         }
  68.         echo $result;
  69.         exit();
  70.     } else {
  71.         echo "Error. Error.  Error. **{$char}** is not a valid symbol. Retry.\n";
  72.         exit();
  73.     }
  74.  
  75. }
Success #stdin #stdout 0.02s 52472KB
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https://ideone.com/PlYb5t
language:
PHP (php 7.3.5)
created:
8 years ago
visibility:
public

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