mysql inserting "--" from datepicker

Hey guys,

i have a weird issue that I have been trying to debug for almost an hour, can't wrap my brain around it.. I am using the Jquery UI datepicker with an input for a birthday, however even when I take this function out I am having issues which leads me to believe that it is something that mysql is doing.. When I try to insert the date into my table i receive the value of "--" instead of the date..my field to is set to VARCHAR which is why I am not understanding why it would be doing this....heres the relevant code.. in snippets

if(preg_match($pattern,$_POST['b_date'],$match)){
$birthday = $match[0]; //set birthday variable from preg_match, this works fine
        }...

$sqlcmd = "INSERT INTO members (first_name, last_name, email, password, b_date, gender, ip, date , randnum, activated)
	VALUES('$firstname','$lastname','$email','$dbpassword','$birthday','$gender','$ipaddress', '$date', '$randnum', 0)";
	$query = mysql_query($sqlcmd) or die (mysql_error()); //inserts the data fine, except for the "--"

comes from this input

<input type="text"  name="b_date" id="birthday" class="input_search_text2" />	

This sounds a lot like either an escaping issue, or a delimiter problem - what do you get if, you post sample data, as the contents of $birthday and $sqlcmd? 

even if I force the value of $birthday to a string like "08/04/1988" mysql is still inserting "--"..

I have figured this one out, I had a variable from a previous method named $birthday as well that was overwriting my variable...thanks alot for your help