working on a login php form

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HTML

PHP

web_development

here is my error..

Warning: mysql_result() expects parameter 1 to be resource, boolean given in E:\XAMPP\htdocs\basicphpedit\core\functions\users.php on line 6
Array ( [0] => We can't find that username, have you registed? )

<?php
function user_exists($username) 
    { 
        $username = sanitize($username); 
        return (mysql_result(mysql_query("SELECT COUNT ('id') FROM 'practice' WHERE 'login' = '$username'"), 0) == 1) ? TRUE : FALSE; 
    }            //    "SELECT COUNT ('id') FROM 'practice' WHERE 'login' = '$username'"), 0) == 1) ? TRUE : FALSE; 
     
     
    function user_active($username) 
    { 
        $username = sanitize($username); 
        return (mysql_result(mysql_query("SELECT COUNT ('id') FROM 'practice' WHERE 'login' = '$username' AND 'active' = 1"),0)===1)?TRUE:FALSE; 
    } 

    function id_from_username($username) 
    { 
        $username = sanitize($username); 
        return mysql_result(mysql_query("SELECT 'id' FROM 'practice' WHERE 'login'='$username'"),0,'id'); 
    } 
     
     
    function login($username, $password) 
    { 
        $user_id = id_from_username($username); 
         
        $username = sanitize($username); 
        //$password = md5($password); 
         
        return (mysql_result(mysql_query("SELECT COUNT('id') FROM 'practice' WHERE 'login'='$username' AND 'password'='$password'"),0)==1) ?$user_id : FALSE; 
    } 
?>