Undefined variable

[codingin]

I have connected to database link below

$db_host     = "localhost";
 $db_username = "root";
 $db_password = "";
 $db_name     = "db"; 


$sql = new mysqli($db_host,$db_username,$db_password,$db_name);

And I refered to it on a different page like:

function user_exists($username){
     $username = sanitize($username);
     $query_user = $sql->query("SELECT COUNT(`user_id`) FROM `users` WHERE `username` = '$username'");
     return (mysqli_result($query_run,0)==1)? true:false;
 }

But I still receive:
undefined variable sql,
What am I missing?

[diafol]

WHy are you creating a mysqli object and then ignoring it with mysqli_result? WHere is $query set?

[codingin]

Alternatively, I did something like below, I had the same error: undefined variable sql

$db_host = 'localhost';
$db_username = 'root';
$db_password = '';
$db_name = 'db';

$sql = mysqli_connect($db_host,$db_username,$db_password,$db_name);

$query = mysqli_query($sql,"SELECT");

return (mysqli_result($query,0)===1)?true:false;

Using the Object

$db = new mysqli($db_host,$db_username,$db_password,$db_name);
$query = $db->query("SELECT things FROM table WHERE something = '$something'");
return ($query->result(0)===1)?true:false;

Is this correct?

[diafol]

return should only be used inside a function or class method. Is this in a function or class method?

What does $query->result try to do? Are you looking for num_rows?

One problem that you have is that your object naming is ambiguous.

$query suggests a statement, whereas you're actually storing the resultset in it. It would probably be best to call it $result.

In addition, you are injecting variables directly into the SQL. While this may be OK for trusted values, why not take advantage of prepared statements?

[codingin]

Some of the queries are only to validate the availability of a user in the database, and you're right, these only check the num_rows to see if users is available or. Other queries are what I want to echo to the users which demands the mysql_fetch_assoc

I want to connect to database uisng mysqli instead of mysql, which means the queries and functions must use the mysqli.

my main problem is converting mysql_results, eg below

$db_host     = "localhost";
 $db_username = "username";
 $db_password = "password";
 $db_name     = "db_name";

mysqli_connect($db_host,$db_username,$db_password);
mysql_select_db($db_name);

function email_exists($email){
  $email =sanitize($email)
   $query = mysql_query(SELECT user_id FROM users WHERE email = '$email'");
    return (mysql_result($query,0)===1)?true:false;// here
 }

Connecting to database using mysqli procedural.

$mysqli = mysqli_connect($db_host,$db_username,$db_password,$db_name);

function email_exists($email){
$email = sanitize($email);
 $query = mysqli_query($sql,"SELECT COUNT(user_id) FROM table WHERE email = '$email'");
 return(//here is the problem since there isn't mysqli_result function);
}

Connecting using Object

$mysqli = new mysqli($db_host,$db_username,$db_password,$db_name);

function email_exists($email){
 $email = sanitize($email);
$query = $mysqli->query("SELECT COUNT(user_id) FROM users WHERE email = '$email'");
return ($query->????????) // here is the problem. I have been scouring the net for solution but to no avail.
}

Thanks for your help