jQuery causing my php to break - php

Question

I'm working on an online booking system, so I have a php script that receives a date and will output an array of possible timeslots that are free on that date. I'm trying to make it so that when closing the datepicker it sends the variables to the file and retrieves the result. At the moment the submit button also leads to the php file, and will show me available slots when I choose a date. The php part works, but when I add events to the datepicker it won't submit any variables to the php file. I think this is also the cause that when I add another load.('input_date.php'); I get the full timeslot list caused by the if(isset... Can anyone tell me why jQuery is ruining my variable posting? Thanks in advance..
$(document).ready(function() {
$("#dates").load('input_date.php');
$("#datepicker").datepicker({onClose: function() {
$.post("input_date.php", $('#datepicker').serialize());
alert(1);
}});
});
This is the php file:
<?php
include('connection.php');
error_reporting(0);
$treatment = $_POST['treatment'];
$bookdate = $_POST['bookdate'];
if(isset($treatment) && isset($bookdate)){
$exp = explode("-", $bookdate);
//determine what day of the week it is
$timestamp = mktime(0,0,0,$exp[1],$exp[0],$exp[2]);
$dw = date( "w", $timestamp); // sun0,mon1,tue2,wed3,thur4,fri5,sat6
echo $dw."weekday"; //week day
echo"<br/>";
//find bookings with same date
$q = mysql_query("SELECT BOOK_SLOT_ID FROM BOOKINGS WHERE BOOK_DATE='$bookdate'");
//make array of booking slots
$array1 = array();
while ($s = mysql_fetch_array($q)) {
$array1[] = $s['BOOK_SLOT_ID'];
}
$q2 = mysql_query("SELECT SL_ID FROM SLOTS");
//make array of all slots
$array2 = array();
while ($s2 = mysql_fetch_array($q2)) {
$array2[] = $s2['SL_ID'];
}
//remove bookings from all slots
$arr_res = array_diff($array2, $array1);
//make selectable options of results
echo "<SELECT>";
foreach($arr_res as $op){
$r = mysql_query("SELECT SL_TIME FROM SLOTS WHERE SL_ID='$op'");
$q3 = mysql_fetch_array($r);
echo "<OPTION value=".$op.">".$q3['SL_TIME']."</OPTION>";
}
echo "</SELECT>";
}else{
$else = mysql_query("SELECT * FROM SLOTS");
echo "<SELECT>";
while($array_else = mysql_fetch_array($else)){
echo "<OPTION value=".$array_else['SL_ID'].">".$array_else['SL_TIME']."</OPTION>";
}
echo "</SELECT>";
}
?>

Answer 1

I believe it is because you have this line of code:
$('#datepicker').serialize()
This should be changed to the id of the form not the datapicker. In your PHP you are trying to get two seperate values:
$treatment = $_POST['treatment'];
$bookdate = $_POST['bookdate'];
Right now you are just sending the value of the input field #datepicker.