Selectbox selected

I choose something from selectbox and click on the button and i get list of the data from database but, whatever i choose from selectbox doesn't remain what i have chosen. It sets itself to first value. How can i do "selected" ?

<?php
$mysqli = new mysqli("localhost","root","","inantest");
if (mysqli_connect_errno()) {
	printf ("Connection failed : %s\n", mysqli_connect_error());
	exit();
	}

	if ("Ara" == $_POST["iller"]) {
		//$select = "selected=\"Selected\"";
		$aranacakIl=$_POST["selectIl"];
		
		$sql = "SELECT * FROM plaka WHERE ilName= '$aranacakIl' "; 
		$calistir = mysqli_query($mysqli, $sql);

		if ($calistir) {
			while ($newArray = mysqli_fetch_array ($calistir, MYSQLI_ASSOC)) {
				$plaka = $newArray['ilPlaka'];
			}
		}

		$sql = "SELECT * FROM ilce WHERE ilPlaka= '$plaka' "; 
		$calistir = mysqli_query($mysqli, $sql);

		if ($calistir) {
			while ($newArray = mysqli_fetch_array ($calistir, MYSQLI_ASSOC)) {
				$ilce = $newArray['ililce'];
				print "$ilce<br>";
			}
		}	
	}
?>


<form method="post" action="">
  <select name="selectIl">
<?php
	$sql = "SELECT * FROM il";
	$calistir = mysqli_query($mysqli, $sql);

	if ($calistir) {
		while ($newArray = mysqli_fetch_array ($calistir, MYSQLI_ASSOC)) {
			$il = $newArray['ilName'];
		    printf("<option value=\"$il\">$il</option>");
		}
		//mysqli_free_result($calistir);
		//mysqli_close($mysqli);
	}
?>
  </select>
  <input type="submit" name="iller" value="Ara" />
</form>