Something

<?php
$line = "4 + 5 * 6";
$total = explode(" ",$line);
$i = 0;
$num = 1;
while ($i < count($total)) {
if ($total[$num] == "+") {
$calc = $total[$i] + $total[$i + 2];
$result = $result + $calc;
$i = $i + 3;
$num = $num + 2;
continue;
}
if ($total[$num] == "*") {
$calc = $total[$i] * $total[$i + 2];
$result = $result + $calc;
$i = $i + 3;
$num = $num + 2;
continue;
}
if ($total[$num] == "-") {
$calc = $total[$i] - $total[$i + 2];
$result = $result + $calc;
$i = $i + 3;
$num = $num + 2;
continue;
}
if ($total[$num] == "/") {
$calc = $total[$i] / $total[$i + 2];
$result = $result + $calc;
$i = $i + 3;
$num = $num + 2;
continue;
}
}
echo $result;
?>