<?php
 
error_reporting(-1);
mb_internal_encoding('utf-8');


$strInput = "34-66+32=";
$length = strlen($strInput);
$number = 0; 
$result = 0; 
$op = ''; 

function action($op, $int1, $int2) {
    $result = 0;
    if ($op == "+") {
        $result = $int1 + $int2;
    } elseif ($op == "-") {
        $result = $int1 - $int2;
    } elseif ($op == "*") {
        $result = $int1 * $int2;
    }
    return $result;
}


for ($i = 0; $i < $length; $i++) {
    $char = mb_substr($strInput, $i, 1);
    if (is_numeric($char) && $op == '') {
        
        $result = (($result * 10) + intval($char));

    }

        elseif (is_numeric($char)) {
            $number = (($number * 10) + intval($char));
            var_dump($number);

    }

        elseif ($char == '*' || $char == '+' || $char == '-') {
            if ($op == '') {
                $op = $char;
            } else {
                $result = action($char, $result, $number);
                echo "result is {$result}";
                $op = $char;
                $number = 0;
            }
    } 
        
        elseif ($char == '=') {
            $result = action($op, $result, $number);
            echo $result;
            exit();

    }

        else {
            echo "Wrong symbol: {$char} \n";

    }
}