generating reference id after form submit - php

Question

I am trying to generate a reference id like this CTS-P 0 then CTS-P 1 each time a user submits a form and it gets inserted.
what i have came up with is inserting CTS-P 0 to database as i submit.but the problem is its not incrementing CTS-P 0 to CTS-P 1 after i submit again.
i tried to use mysql_insert_id() here is what i have done so far.this is the smallest thing but i could not solve. please have a look
<?php
$con=mysql_connect("localhost","root","");
mysql_select_db("dbname",$con);
$genid="";
if(isset($_POST['submit'])) {
$frstname=$_POST["frstname"];
$genid=mysql_insert_id();
$genid .=count($genid);
//echo $genid;
for($i=0; $i<$genid; $i++) {
$sql = "INSERT INTO tblname (`namecol`,`refidcol`) VALUES ('$frstname','CTS-P $genid[$i]')";
$result = mysql_query($sql);
}}
?>
//here is the form
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" name="generate" >
First Name<input type="text" name="frstname" />
<input type="submit" name="submit" value="Submit" />
</form>
it is inserting it in my refid column as CTS-P 0 but not incrementing from next time i submit.i know its very noobish but i am stuck.

Answer 1

<?php
$con=mysql_connect("localhost","root","");
mysql_select_db("dbname",$con);
if(isset($_POST['submit'])) {
$frstname=$_POST["frstname"];
$sql = "SELECT * FROM tblname";
$genid = mysql_query($sql, $con);
$genid = mysql_num_rows($genid);
//Since you're using "0" as your first number, I decided to comment this out, if not, uncomment it
//$genid++;
$sql = "INSERT INTO tblname (`namecol`,`refidcol`) VALUES ('$frstname','CTS-P $genid')";
$result = mysql_query($sql);
}
?>