PHP警告：mysqli_query（）需要至少2个参数，1 [重复]

I don't know what's wrong and I get an error. Help me. Thank you in advance.

PHP Code

<?php
//DATABASE
$con=mysqli_connect("localhost", "root", "pw1234", "mr_system_db");

if(mysqli_connect_errno($con)) {
    echo "Failed to connect to MySQL: " . mysqli_connect_error();   
}



//$Today = $_POST['today'];


$now_date = date("Y-m-d");
echo $now_date;
//쿼리
$query = "SELECT MR_Dept_TB_Dept_NO, MR_MtRoom_TB_MtRoom_NO, MR_Info_Stime, MR_Info_Etime, mr_info_date
         FROM mr_info_tb where mr_info_date =  '$now_date'";

error point! $result = mysqli_query($query);

mysqli_query() expects at least 2 parameters, 1 given

$result = mysqli_query($query); 

if(!$result ) 

error point * mysqli_error() expects exactly 1 parameter, 0 given

die ( "Database access failed  : "  . mysqli_error());


    while ($row = mysqli_fetch_object($result)) {
        $arr[] = $row;  
    }
    echo json_encode($arr, JSON_UNESCAPED_UNICODE);


    mysqli_free_result($result);
    mysqli_close($con);

?>

</div>

You should change

$result = mysqli_query($query); to $result = mysqli_query($con,$query);

and

mysqli_error() to mysqli_error($con)