Fatal error: Uncaught Error: Call to a member function bind_param() on boolean

[Kiwi_gamer01]

	<form action="playmobil.php" method="POST">
		<table align="center" border="1">
			<tr>
				<th></th>
				<th>Wert</th>
				<th></th>
				<th>INTO</th>
				<th></th>
				<th>ID</th>
				<th></th>
				<th>Senden</th>
			</tr>
			<t>
				<td><b>UPDATE playmobil SET</td>
				<td><input type="text" name="Wert" /></td>
				<td><b>=</td>
				<td><input type="text" name="into" /></td>
				<td><b>WHERE ID =</td>
				<td><input type="int" name="ID2" /></td>
				<td><b>;</td>
				<td><input type="submit" name="submit2" value="Senden" /></td>
			</t>
		</table>
	</form>	
<?php
	if(isset($_POST["submit2"])):
	
		echo $_POST["Wert"];
		echo $_POST["into"];
		echo $_POST["ID2"];
		
		$Wert = $_POST["Wert"];
		$into = $_POST["into"];
		$ID2 = $_POST["ID2"];
	
		$absenden2 = $mysqli->prepare("UPDATE playmobil SET ? = '?' WHERE ID=?");
		$absenden2->bind_param("ssi", $Wert, $into, $ID2);               <!-- Zeile 150-->
		$absenden2->execute();
		$absenden2->close();
endif;		

Warum erhalte ich diese Fehlermeldung

Fatal error: Uncaught Error: Call to a member function bind_param() on boolean in D:\Programme\XMAPP\htdocs\playmobil.php:150 Stack trace: #0 {main} thrown in D:\Programme\XMAPP\htdocs\playmobil.php on line 150