<?php
$exp = "62*2+15634=";
$number = 0;
$op;
$falg = false;
$result = 0;
for($i = 0; $i < strlen($exp); $i++) {
    if(!is_numeric($exp[$i])) {
        if ($flag) {
            $result = eval("return {$result} $op {$number};");
            $op = $exp[$i];
            $number = 0;
            if($op == "=") {
                echo "$result";
                exit();
            }
        }
        else {
            $op = $exp[$i];
            $flag = true;
            $result = $number;
            $number = 0;
        }
    }
    else {
        $number = 10 * $number + $exp[$i];
    }
}

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