<?php
 
$input = '2+2*2-2=';
$inputLenght = strlen($input);
 
$number = 0;
$result = 0;
$op = '';
 
for($i = 0; $i < $inputLenght; $i++) {
	$char = substr($input, $i, 1);
		if($char == '*' || $char == '+' || $char == '-' ||$char == '=') {
		$op = $char;
		if($op == '*'){
			$result = $result * $number;
			}
				if($op == '+'){
			$result = $result + $number;
			}
 
			if($op == '-'){
			$result = $result - $number;
			}
 
			if($op == '='){
			echo $result;
			exit;
			}
		}
		elseif (is_numeric($char)) {
			$z = intval($char);
			$number = $number * 10;
			$number = $number + $z;
		}
}