<?php

function checkDiscountEligibility($age, $membership) {

    $age = trim($age);
    $membership = strtolower(trim($membership));

-    if (empty($age) || !is_numeric($age)) {
        return "Invalid age input. Please enter a numeric value.";
    }

    if ($membership !== "yes" && $membership !== "no") {
        return "Invalid membership input. Please enter 'yes' or 'no'.";
    }

    $age = (int)$age;

    if ($age < 18) {
        return "Eligible for Youth Discount";
    } elseif ($age >= 65) {
        return "Eligible for Senior Citizen Discount";
    } elseif ($age >= 18 && $age <= 64 && $membership === "yes") {
        return "Eligible for Member Discount";
    } else {
        return "No discount available";
    }
}

$age = $_POST['age'] ?? '';
$membership = $_POST['membership'] ?? '';

echo checkDiscountEligibility($age, $membership);
?>