' field below. // Please check man page for isset function. $submitted = isset($_GET['submitted']); if ($submitted) { echo '

This is the result:

'; $a = $_GET['A_value']; $op = $_GET['operation_value']; $b = $_GET['B_value']; if ($op == '+') $result = $a + $b; if ($op == '-') $result = $a - $b; if ($op == '*') $result = $a * $b; if ($op == '/') { if ($b == 0) { $result = 'inf'; } else { $result = $a / $b; } } if ($op == '^') $result = $a ** $b; echo "$a $op $b = $result

"; } else { echo '

This calculator computes A operation B:

A:
operation:
B:
'; } ?>