Php 如何使用多个表单验证复选框？

我有3张表格和一个复选框，如下所示：

<input type="checkbox" name="confirm_agreement" value=yes <?php if (isset($_POST["confirm_agreement2"])) {print "checked";}?>>I agree

<form action="https://www.paypal.com/webscr" method="post">
      <input type="image" src="https://www.paypal.com/en_US/x-click-but02.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
       <input type="hidden" name="cmd" value="_xclick-subscriptions">
       <input type="hidden" name="business" value="paypal@exploretalent.com">
       <input type="hidden" name="no_shipping" value="1">
       <input type="hidden" name="no_note2" value="1">
       ...
       <input type="hidden" name="sra" value="1">
</form>

<form action="https://www.paypal.com/webscr" method="post">
      <input type="image" src="https://www.paypal.com/en_US/x-click-but02.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
       <input type="hidden" name="cmd" value="_xclick-subscriptions">
       <input type="hidden" name="business" value="paypal@exploretalent.com">
       <input type="hidden" name="no_shipping" value="2">
       <input type="hidden" name="no_note2" value="2">
       ...
       <input type="hidden" name="sra" value="2">
</form>

<form action="https://www.paypal.com/webscr" method="post">
      <input type="image" src="https://www.paypal.com/en_US/x-click-but02.gif" border="0" name="submit" alt="Make payments with PayPal - it's fast, free and secure!">
       <input type="hidden" name="cmd" value="_xclick-subscriptions">
       <input type="hidden" name="business" value="paypal@exploretalent.com">
       <input type="hidden" name="no_shipping" value="2">
       <input type="hidden" name="no_note2" value="2">
       ...
       <input type="hidden" name="sra" value="2">
</form>

然后在表单上添加

onsubmit=“return checkbox（）；”

，但这不起作用

关于如何做到这一点有什么想法吗

---

谢谢

你也可以这样做

function checkCheckBoxes() {
if (document.getElementsByName('confirm_agreement')[0].checked == false)
{
    alert ('You must agree with the User Agreement Terms!');
    return false;
}
}

---

这是一行截取的jQuery，类似于

$（'form'）.submit（函数（）{if（！$（'confirm#u agreement'）.is（'checked'））{alert（'You must check the box'）；return false}）

function checkCheckBoxes() {
if (document.getElementsByName('confirm_agreement')[0].checked == false)
{
    alert ('You must agree with the User Agreement Terms!');
    return false;
}
}