alert once submit button clicked and checkbox is empty

[robert_gsfame]

Can anyone help me? i would like to give some alert once submit button was clicked and (!isset($_POST['checkbox']))

 

thx

[Scotty2024]

if(isset($_POST['submit']))
{
   if(isset($_POST['checkbox']))
   {
      //proceed
   }
   else
   {
      $checkBoxFlag = true;
   }
}

//at your form or wherever
if($checkBoxFlag)
{
   echo 'You must check the checkbox';
}
//form code here

[robert_gsfame]

this is not what i'm looking for... i want create an alert in javascript

 

[Scotty2024]

if(isset($_POST['submit']))
{
   if(isset($_POST['checkbox']))
   {
      //proceed
   }
   else
   {
      $checkBoxFlag = true;
   }
}

//at your form or wherever
if($checkBoxFlag)
{
   ?>
      <script type="text/javascript">
      alert("You must check the checkbox");
      </script>
   <?PHP
}
//form code here

[robert_gsfame]

not even that... when i use that code tjen the alert will come together with a blank page

 

i want have it in javascript function (onclick)

[rajivgonsalves]

onclick of what ? if you post some code we could help

[mikesta707]

create a javascript function that will check if the check box is checked and call that function in the onSubmit attribute of your submit button