How to call an option in php?

[Louloul]

I want to call from a form the radio option and put it in sql(php)
-this is the html code

<input type="radio" name="rb" ID="Radio1" VALUE="Radio1" <select id="Select1" name="Kinder"> 
<option value="1">Nursery</option> 
<option value="2">Kg1</option> 
<option value="3">Kg2</option> 
</select> 
<td>
</tr>
<tr>
<td align=center>
<select name="elem" id="Select2"> 
<option value="1">Grade1</option> 
<option value="2">Grade2</option> 
<option value="3">Grade3</option> 
<option value="4">Grade4</option> 
<option value="5">Grade5</option> 
<option value="6">Grade6</option> 
<option value="7">Grade7</option> 
<option value="8">Grade8</option> 
<option value="9">Grade9</option> 
</select>

-this is the php code

if(isset($_POST["C"]))
$t="document.form.getElementsByTagName('option').value";
$C=$_POST['t'];

include('MySQLConnection.php');
$result=mysql_query("INSRET INTO registration (ID_etu, level_etu, class_etu, section_etu, date_reg ) 
values('', '".$rb."', '".$C."', '".$rd1."', '".$dt."'");
$sql=mysql_query($result. "mysql_error()");
?>

it is giving me an error:

Notice: Undefined index: t in C:\wamp\www\www \Register.php on line 15

Can anyone help? How should I write it?

Thanks for any help

[JKing]

You never closed your input tag in your html.

<input type="radio" name="rb" ID="Radio1" VALUE="Radio1" /> 
<select id="Select1" name="Kinder"> 
<option value="1">Nursery</option> 
<option value="2">Kg1</option> 
<option value="3">Kg2</option> 
</select> 
<td>
</tr>
<tr>
<td align=center>
<select name="elem" id="Select2"> 
<option value="1">Grade1</option> 
<option value="2">Grade2</option> 
<option value="3">Grade3</option> 
<option value="4">Grade4</option> 
<option value="5">Grade5</option> 
<option value="6">Grade6</option> 
<option value="7">Grade7</option> 
<option value="8">Grade8</option> 
<option value="9">Grade9</option> 
</select>

Form values are passed to the $_POST[] variable.
You access those values by their name.
For your radio button it would be $_POST['rb']

Any user input should be escaped using mysql_real_esca pe_string() before inserting it into a query to prevent sql injection attacks.

Your error that you are receiving means there is no input with the name of "t".

[Atli]

JKing: You access those values by their ID.

Your error that you are receiving means there is no input with the id of "t".

Don't you mean by their "name"?
It's the "name" attribute of the <input> tag that is used as the element name in the $_POST or $_GET arrays, not the "id" attribute.

[JKing]

Yes that is what I mean. Thank you for spotting the mistake.

[Dormilich]

You never closed your input tag in your html.

input elements must not be closed in HTML.

[JKing]

It would still require the closing angle bracket.

[kovik]

Self-closing tags are still closed. :P

[Atli]

He means, the OP fails to close the elements themselves.
[code=html]
<input type="whatever" <select ...>

<-- Should be -->

<input type="whatever" ><select ...>
[/code]