Checking seat numbers correctly in MySql table - php

Question

I am developing a script for a table called 'minivan'. Here is the table structure sql fiddle link. Admin provides seats for minivan.
I want to check if seats are available from this search form: search form link The method is GET.
First i want to check the date [this is format of date: 2015-02-16 for example] that a user submits. If the date matches i want to proceed with 'from' and 'to' location that a user chooses. If records are found i want to check what is the total passenger from the dropdown list for different ages that a users provides.
If the total number of passenger does not exceed the seat number for a particular day that a user chooses, i want to echo "seats are available". and proceed with other parts that i am planning to develop later.
<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "test";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if (!$conn) {
die("Connection failed: " . $conn->connect_error);
}
if (isset($_GET['submit'])) {
$date = $_GET['date_up'];
$query = "SELECT date_up FROM minivan WHERE date_up = '$date'";
$result = mysqli_query($conn, $query);
$numrows = mysqli_num_rows($result);
//print_r($numrows);
if ($numrows)
{
$startPlace = $_GET['startpoint'];
$query2 = "SELECT startpoint FROM minivan WHERE startpoint = '$startPlace'";
$result2 = mysqli_query($conn, $query2);
//print_r($result2);
$numrows2 = mysqli_num_rows($result2);
$endPlace = $_GET['endpoint'];
$query3 = "SELECT endpoint FROM minivan WHERE endpoint = '$endPlace'";
$result3 = mysqli_query($conn, $query3);
//print_r($result2);
$numrows3 = mysqli_num_rows($result3);
if ($numrows2 && $numrows3) {
$adult = $_GET['adult'];
$juvenile = $_GET['juvenile'];
$kids = $_GET['kids'];
$child = $_GET['child'];
$totalPassenger = $adult + $juvenile + $kids + $child ;
$seatQuery = "SELECT seat FROM minivan WHERE seat > $totalPassenger";
$result4 = mysqli_query($conn, $seatQuery);
$numrows4 = mysqli_num_rows($result4);//shows error here how to fix it?
if ($numrows4) {
while ($row = mysqli_fetch_row($result4)) {
$seats = $row[0];
echo "$seats are availble for the $date you selected";
}
} else {
echo "no seats are found";
}
}
} else {
"start point and end point does not match";
}
}
$conn->close();
?>
It shows error here $numrows4 = mysqli_num_rows($result4);//shows error here how to fix it?
here is the form i am trying to search with
<form action="" method="GET">
From
<select name="startpoint" id="from">
<option >Hat Yai Airport</option>
<option >Pak Bara</option>
<option >Kohlipe</option>
</select>
To
<select name="endpoint" id="to">
<option >Pak Bara</option>
<option >Hat Yai Airport</option>
<option >Kohlipe</option>
</select>
<label for="Date">Date</label>
<input type="text" name="date_up" id="datepicker">
<h4 style="margin-top: 30px;">Passengers</h4>
Adults
<select name="adult" id="from">
<option >1</option>
<option >2</option>
<option >3</option>
<option >4</option>
<option >5</option>
</select>
< 12 years
<select name="juvenile" id="to">
<option >0</option>
<option >1</option>
<option >2</option>
<option >3</option>
<option >4</option>
</select>
< 7 years
<select name="kids" id="from">
<option >0</option>
<option >1</option>
<option >2</option>
<option >3</option>
</select>
< 3 years
<select name="child" id="to">
<option >0</option>
<option >1</option>
<option >2</option>
<option >3</option>
</select>
<input type="submit" value="Search" class="submit" name="submit">
Can't really figure out whats wrong with this. I am beginner in php and mysql. Please help me solve this.