在null上调用成员函数query（）

Question

我的PHP文件存在奇怪的问题，我在数据库中添加了一些东西。我刚刚在我的服务器上安装了php7（安装PHP 5.6时一切正常）我收到错误：

  

PHP消息：PHP致命错误：未捕获错误：呼叫成员   函数query（）在/srv/patch/newDB.php:26

上的null

newDB文件。

<?php
session_start();
require_once 'connectDB.php';

$data = json_decode(file_get_contents("php://input"));

$username = mysqli_real_escape_string($connect, $data->username);
$task = mysqli_real_escape_string($connect, $data->task);
$dept = mysqli_real_escape_string($connect, $data->dept);
$state = mysqli_real_escape_string($connect, $data->state);
$task_start = mysqli_real_escape_string($connect, $data->task_start);
$task_end = mysqli_real_escape_string($connect, $data->task_end);
$login = mysqli_real_escape_string($connect, $data->login);
$deadline = mysqli_real_escape_string($connect, $data->deadline);
$priority = mysqli_real_escape_string($connect, $data->priority);

if($_SESSION['type']=='Admin') {
       $query = "INSERT into tasks_main (username,task,dept,status,task_start,task_end,deadline,task_time,priority) VALUES ('$login','$task','$dept','$state','$task_start','$task_end','$deadline','$task_time','$priority')";          
}else {
    $query = "INSERT into tasks_main (username,task,dept,status,task_start,task_end,deadline,task_time,priority) VALUES ('$username','$task','$dept','$state','$task_start','$task_end','$deadline','$task_time','$priority')";
}

mysqli_query($connect, $query);

echo true;
mysqli_close($connect);
?>