Mysql警告错误[重复]

I got this below warning while executing the code. How to overcome that warning error. Warning: mysql_result() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\login®ister\core\function\users.php on line 6.

<?php
function user_exists($username)
{
    $username = sanitize($username);
$query=mysqli_query("SELECT COUNT (`user_id`) FROM  `users` WHERE `username`='$username' ");
return (mysqli_result($query, 0)==1) ? true : false ;

}

function user_active($username)
{
    $username = sanitize($username);
$query=mysqli_query("SELECT COUNT (`user_id`) FROM  `users` WHERE `username`='$username' AND `active`=1  ");
return (mysql_result($query, 0) ==1 ) ? true : false ;

}
?>

</div>

The procedural style of mysqli_query requires a link identifier as first parameter.

mysqli_query($link, 'query here');

Don't forget you're inside a function there as well, any $link set outside the function is unknown inside the function.