papar sql berasaskan bulan dan tahun

searchdate.php

<form method="GET" action="searchdate.php">
search by Year <select id="year" name="year">
<option value="">All</option>
<?php
for($i=2015;$i < date("Y")+1; $i++)
{
	echo '<option value="'.$i.'">'.$i.'</option>';
}
?>
</select><input type="submit" value="submit" name="submit">

search by Month <select id="month" name="month">
<option value=""></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>

</select>

<input type="submit" value="submit" name="submit">
</form>
<?php
if (isset($_GET['year']))
{
	$year = isset($_GET['year']) ? $_GET['year'] : '';
	$month = isset($_GET['month']) ? $_GET['month'] : '';

	$sql = "SELECT * FROM sales
	WHERE YEAR(date) = '$year'
	AND MONTH(date) = '$month' ";

	echo $sql;
}