Using MX | PHP | MySQL

I'm new to PHP and trying to insert insert values into a MySql DB where two of the fields are dates. (startDate and endDate) Those two date values are passed to to the form as URL variables and populate the fields when the page is displayed. I need to use the split function to take the date in mm/dd/yyyy format and enter it into the DB in yyyy-mm-dd format. Could someone take a look at my code and see if I'm on the right track? Thanks!

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$startDate = '01/01/2007';
if (isset($HTTP_GET_VARS['startDate'])) {
$startDate = (get_magic_quotes_gpc()) ? $HTTP_GET_VARS['startDate'] :
stripslashes($HTTP_GET_VARS['startDate']);
}
list($sMonth, $sDay, $sYear) = split('[/.-]', $startDate);
if (is_numeric($sMonth) && is_numeric($sDay) && is_numeric($sYear)) {
$sDate = "$sYear-$sMonth-$sDay";
}
else {
echo 'Invalid start date';
exit;
}

$endDate = '01/02/2007';
if (isset($HTTP_GET_VARS['endDate'])) {
$endDate_rsAV = (get_magic_quotes_gpc()) ? $HTTP_GET_VARS['endDate'] :
stripslashes($HTTP_GET_VARS['endDate']);
}
list($eMonth, $eDay, $eYear) = split('[/.-]', $endDate);
// check that date elements are all numbers
if (is_numeric($eMonth) && is_numeric($eDay) && is_numeric($eYear)) {
$eDate = "$eYear-$eMonth-$eDay";
}
else {
echo 'Invalid end date';
exit;
}

if ((isset($HTTP_POST_VARS["MM_insert"])) && ($HTTP_POST_VARS["MM_insert"] == "bookroom") {
$insertSQL = sprintf("INSERT INTO bookings (roomID, clientID, startDate, endDate, adults, children) VALUES (%s, %s, %s, %s, %s, %s)",
GetSQLValueString($HTTP_POST_VARS['roomID'], "text",
GetSQLValueString($HTTP_POST_VARS['clientID'], "text",
GetSQLValueString($HTTP_POST_VARS['$sDate'], "date",
GetSQLValueString($HTTP_POST_VARS['$eDate'], "date",
GetSQLValueString($HTTP_POST_VARS['adults'], "int",
GetSQLValueString($HTTP_POST_VARS['children'], "int");

mysql_select_db($database_connGR, $connGR);
$Result1 = mysql_query($insertSQL, $connGR) or die(mysql_error());
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