mysqli_stmt_bind_param不能处理时间类型吗？解决思路

mysqli_stmt_bind_param($stmt, 'idii', $c, $a, $t, $w);

require ('inc/config.php');
$page_title = '住宅数据添加-feige数据中心';
include ('inc/header.php');
require (MYSQL);
if ($_SERVER['REQUEST_METHOD'] == 'POST') {	
	$trimmed = array_map('trim', $_POST);
	$errors = array();
	if(empty($trimmed['wdate'])) {
		$errors[] = '日期不能为空';
	} else {
		$w = mysqli_real_escape_string ($conn, $trimmed['wdate']);
	}
	
	if ( isset($trimmed['city']) && filter_var($trimmed['city'], FILTER_VALIDATE_INT, array('city' => 1)) ) {
		$c = mysqli_real_escape_string ($conn, $trimmed['city']);;
	} else {
		$errors[] = '请选择区域';
	}
	
	if (is_numeric($trimmed['taoshu']) && ($trimmed['taoshu'] > 0)) {
		$t = mysqli_real_escape_string ($conn, (int) $trimmed['taoshu']);
	} else {
		$errors[] = '请输入一个正确的套数';
	}
	if (is_numeric($trimmed['area']) && ($trimmed['area'] > 0)) {
		$a = mysqli_real_escape_string ($conn, (float) $trimmed['area']);
	} else {
		$errors[] = '请输入一个正确的面积';
	}
	
	
	if (empty($errors)) {
		$q = 'INSERT INTO f_chengjiao (city_id, area, taoshu, fang_time, os_time) VALUES (?, ?, ?, ?, ?, NOW())';
		$stmt = mysqli_prepare($conn, $q);
		mysqli_stmt_bind_param($stmt, 'idii', $c, $a, $t, $w);
		mysqli_stmt_execute($stmt);

		if (mysqli_stmt_affected_rows($stmt) == 1) {
			echo '
这条数据已经被添加
';
			$_POST = array();	
		} else {
			echo '
程序发生错误，请重新添加
'; 
		}	
		mysqli_stmt_close($stmt);	
	}	
} 

if ( !empty($errors) && is_array($errors) ) {
	echo '
发生下列错误:
';
	foreach ($errors as $msg) {
		echo " - $msg
\n";
	}
	echo '请在试一遍
';
}

?>

	住宅数据添加
	
	
    

include ('inc/footer.php');
?>

出错文件是 'D:\wamp\www\zhuzhai_add.php' 出错行号是 36: mysqli_stmt_bind_param() expects parameter 1 to be mysqli_stmt, boolean given