Getting users data from same field - php

Question

So, I'm writing an application in PHP and I'm trying to retrieve unique user data based on what they entered. Here is my code:
function hello($username123) {
// Connect to Database //
$host3 = "db";
$username3 = "db";
$password3 = "db";
$db3 = "db";
$con3 = mysqli_connect($host3,$username3,$password3,$db3) or die("Can not connect to Server.");
$student1name;
$query3 = mysqli_query($con3,"SELECT * FROM 'users' WHERE 'username' = '$username123' and '$student1name' = 'student1'");
return "$student1name";
}
So, the user enters there username which they registered earlier on and then I run a query where the username field is equal to the username variable (The input) and that the student1name variable is equal to the student1 field where the username is the same as the one entered. I then return the student1name variable. But when I test this all that returns is "". I can't figure out the problem

Answer 1

You must bind the result in a result array and access it like that, something like this should work:
return $query3["student1name"];
Would probably be more effective.
If you're only selecting ONE variable in your query then you can simply echo $query3.
It would also be more effective if you'd look into prepared statements.
Note that
$student1name
doesn't do anything since you never give it a proper value.

Answer 2

you are not fetching the results of the query, try something like this after your query..
$row = mysqli_fetch_array($query3, MYSQLI_ASSOC);
return $row['studentname'];
i'm assuming the student's name is in a column called studentname in your DB

Answer 3

PHP automatically replaces any variables you use inside a string to the value of that variable. For example, if $student1name = 'foo' then putting $student1name anywhere in your SELECT statement literally outputs you a string 'foo' in place of that variable. As far as the mysqli statement is concerned, you aren't using a PHP value, you are using a literal string 'foo'. Therefore, expecting your $student1name var to magically change based on the sql statement isn't going to happen.
To retrieve a column's value you will need to fetch the result rows after you perform the query:
if ($row = $query3->fetch_assoc()) {
return $row["student1"];
}
If you are expecting more than one result row, then you just need to call fetch_assoc() again for each row until it returns you nothing (marking the end of the result rows).