<?php

error_reporting(-1);
mb_internal_encoding('UTF-8');

$input = "243+6743-78*2=";
$inputLength = mb_strlen($input);
$number = 0;
$result = 0;
$op = "";

for ($i = 0; $i < $inputLength; $i++) {
	$char = mb_substr($input, $i, 1);
	if ($char == "*" || $char == "+" || $char == "-" || $char == "/") {
		if ($op == "") {
		    $result = $number;
		} elseif ($op == "*") {
			$result = $result * $number;
		} elseif ($op == "+") {
			$result = $result + $number;
		} elseif ($op == "-") {
			$result = $result - $number;
		} elseif ($op == "/") {
			$result = $result / $number;
		}
		$number = 0;
        $op = $char;
        } elseif (is_numeric($char)) {
	    	$number = $number * 10 + intval($char);
	    } elseif ($char == "=") {
			if ($op == "+") {
				$result = $result + $number;
			} elseif ($op == "*") {
				$result = $result * $number;
		    } elseif ($op == "-") {
				$result = $result - $number;
 			} elseif ($op == "/") {
				$result = $result / $number;
 			}
		} else {
	        echo "Неверный символ: \"$char\". Калькулятор не может обрабатывать подобные символы!\n";
	        exit();
	    }
} 			   

echo "{$input}{$result}\n";
            
?>