在登录时选择语句。 查询失败

Question

This is my code for check login. It return query failed. I don't know which syntax is wrong. Any help ? Do I need to SELECT everything in my table only ? In my login page, there are only need username, password and role. But in my table there are other things to as stated at my $_SESSION below. Do I need to call back everything in my table or something ? Because my coding can't read the query. There is no syntax error but when I try to login, query failed appear.

<?php
session_start();
require 'database.php';

//to store validation errors
$errmsg_arr = array();

//validation error flag
$errflag = false;

//function to sanitize values from the form. Preventing the SQL injection
function clean ($str){
    $str = @trim($str);
    if (get_magic_quotes_gpc()){
        $str = striplashes ($str);
    }
    return mysql_real_escape_string($str);
}

//sanitize POST values
$myusername = clean ($_POST['username']);
$mypassword = clean ($_POST['password']);
$role = clean ($_POST['role']);

//input validations
if ($myusername = ''){
    $errmsg_arr[] = 'Insert your username';
    $errflag = true;
}
if ($mypassword = ''){
    $errmsg_arr[]= 'Insert you password';
    $errflag = true;
}

//if there are input validation, redirect back to home
if ($errflag){
    $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
    session_write_close();
    header("location:index.php");
    exit();
}

$qry = "SELECT user_id, username, name, password, role FROM student WHERE username = '$myusername', password = '".md5($_POST['password'])."' AND role = '$role' ";
$result = mysql_query($qry);

if ($result){
    if (mysql_num_rows($result)== 1){

        session_regenerate_id();
        $student = mysql_fetch_assoc($result);  
        $_SESSION['SESS_USER_ID']= $student['user_id'];
        $_SESSION['SESS_NAME']= $student['name'];
        $_SESSION['SESS_GENDER']= $student['gender'];
        $_SESSION['SESS_MATRIC']= $student['matric'];
        $_SESSION['SESS_COLLEGE']= $student['college'];
        $_SESSION['SESS_FACULTY']= $student['faculty'];
        $_SESSION['SESS_COURSE']= $student['course'];
        $_SESSION['SESS_EMAIL']= $student['email'];
        $_SESSION['SESS_PHONE']= $student['phone'];     
        session_write_close();
        header("location: profile.php");
        exit();
    }else {
        header ("location: login_failed.php");
        exit();
    }
}else {
    die ("Query failed");
}
?>

Answer 1

Try using and instead of , between username and password

WHERE username = '$myusername' and  password = '".md5($_POST['password'])."' AND role = '$role'

instead of

WHERE username = '$myusername', password = '".md5($_POST['password'])."' AND role = '$role'

PHP

 $result = mysql_query($qry) or die (mysql_error());
 if (mysql_num_rows($result) > 0){

    session_regenerate_id();
    $student = mysql_fetch_assoc($result);  
    $_SESSION['SESS_USER_ID']= $student['user_id'];
    $_SESSION['SESS_NAME']= $student['name'];
    $_SESSION['SESS_GENDER']= $student['gender'];
    $_SESSION['SESS_MATRIC']= $student['matric'];
    $_SESSION['SESS_COLLEGE']= $student['college'];
    $_SESSION['SESS_FACULTY']= $student['faculty'];
    $_SESSION['SESS_COURSE']= $student['course'];
    $_SESSION['SESS_EMAIL']= $student['email'];
    $_SESSION['SESS_PHONE']= $student['phone'];     
    session_write_close();
    header("location: profile.php");
    exit();
}else {
    header ("location: login_failed.php");
    exit();
}

NOTE: Use mysqli_* functions or PDO instead of mysql_* functions(deprecated)