A stack machine is a simple system that performs arithmetic operations on an input string of numbers and operators

Simply to add a dependency on piranon/stack-machine to your project's composer.json file.

{
    "require": {
        "piranon/stack-machine": "1.0.*"
    },
    "repositories": [
        {
            "type": "vcs",
            "url":  "[email protected]:piranon/stack-machine.git"
        }
    ]
}

<?php

$stackMachine = new \StackMachine\StackMachine();
$result = $stackMachine->solution('13+62*7+*');

var_dump($result);