Make Required fields in php form

please ..

i have this php form

<FORM action="add.php" method="post">
<TABLE width="100%" border=0>
  <TBODY>
  <TR>
    <TD align=center><FONT color=#ff0000>* </FONT>title:<BR><INPUT size=40
      name=title><BR></TD>
    </TR>
      </TBODY>
      <TABLE width="100%" border=0>
       <TBODY>
       <TR>
       <TD align=center><FONT color=#ff0000>* </FONT>Url<BR><INPUT size=40
      name=url value=http://><BR><TD></TR></TBODY></TABLE>
      </TD>
    </TR>
     <TABLE width="100%" border=0>
       <TBODY>
       <TR>
       <TD align=center>description<BR>
       <textarea cols="50" rows="4" name="description"></textarea><BR><TD></TR></TBODY></TABLE>
      </TD>
    </TBODY></TABLE>
    <P style="TEXT-ALIGN: center" align=center><INPUT class=submit type=submit value="add" name=send></TD>
</FORM>

Code (markup):

and i want make the first 2 fields required ( title and url )

but i want the user don't leave the form if this 2 fields empty ..

i need the user don't go the add.php if this fields empty

or get Pop-up message .. like :: please fill the blank fields

so can anyone help me ..

 

you can do it from the back end or from javascript

 

can you tell me How ?? please

 

if(isset($_REQUEST['add'])
{
$error = 0;
$error_msg = '';

if(!isset($_POST['title'] || (isset($_POST['title']) && strlen($_POST['title']) == 0))
{
$error++;
$error_msg .= 'You did not enter the title<br />';
}

if(!isset($_POST['url'] || (isset($_POST['url']) && (strlen($_POST['url']) == 0 || $_POST['url'] == 'http://')))
{
$error++;
$error_msg .= 'You did not enter the url<br />';
}

if($error > 0)
{
echo $error_msg;
} else if($error == 0) {
//insert form data into database.
}
}

PHP:

 

If you want to use server side validation (means: user must submit the form first, and PHP analyze the form submitted), use tvoodoo solution. If you want clint site validation (means: when user click submit, the form still not submitted), you can check this page: w3schools.com/jS/js_form_validation.asp