<?php

$example = '4+10+3=';
$number = 0;
$char = 'none';
$op = 'none';
$result = 0;

for ($i=0; ; $i++) {

    $getSingleOne = substr($example, $i, 1);

    if (is_numeric($getSingleOne)) {
        $number = ($number * 10) + intval($getSingleOne);
    } else {
        $char = $getSingleOne;

        if (preg_match('/[+]/', $char) == 1 || preg_match('/none/', $char)) {
            $result += $number;
        } elseif (preg_match('/-/', $char) == 1) {
            $result -= $number;
        } elseif (preg_match('/\//', $char) == 1) {
            $result /= $number;
        } elseif (preg_match('/[*]/', $char) == 1) {
            $result *= $number;
        } elseif (preg_match('/=/', $char) == 1) {
            break;
        }

        $number = 0;
        $op = $char;
    }
}

echo "{$example} {$result}";