PDO fetch multiple records from database - php

Question

I am writing a pretty basic piece of code to fetch one or (in most cases) multiple rows from a mysql database.
function getschema($mysqli){
$id = $_SESSION['user_id'];
$query = $mysqli->prepare("SELECT a.naam
FROM schemes AS a, aankoop AS b
WHERE b.aankoop_username_id = :userid && b.aankoop_schema_id = a.id");
$query->bind_param(':userid', $id, PDO::PARAM_INT);
$query->execute();
$result = $query->fetchAll();
echo ($result);
}
I get the user id from the session and pull the data with the query in the prepared statement.
This statement is correct. I tried it in phpmyadmin and it returns the correct values.
Now I want to use this function in my HTML like so...
<?php echo getschema($mysqli); ?>
But my code does not return a thing, it even messes up the layout of my html page where I want to show the code.
I think it probably is something with the fetchAll command. I also tried the PDO::Fetch_ASSOC but that did not work either.
In addition, I cannot see the php errors, even when they are enabled in the php.ini file.

Answer 1

Here's what's going on; you're mixing MySQL APIs/functions and those do not intermix.
Replace the :userid (PDO) bind in b.aankoop_username_id = :userid with a ? placeholder
b.aankoop_username_id = ?
Then this line:
$query->bind_param(':userid', $id, PDO::PARAM_INT);
Replace :userid by $id and remove , PDO::PARAM_INT but adding i
$query->bind_param("i", $id);
Sidenote: Make sure that column is int type. If not, use s instead of i.
Replace the line for fetchAll with the loop as outlined in AbraCadaver's answer.
You can't mix MySQL APIs/function, read the following on Stack:
Can I mix MySQL APIs in PHP?
Read up on mysqli with prepared statements and how it works:
http://www.php.net/manual/en/mysqli.quickstart.prepared-statements.php
Checking for errors would have outlined the errors.
http://php.net/manual/en/mysqli.error.php
http://php.net/manual/en/function.error-reporting.php

Answer 2

Instead of echo ($result); do return $result; in your function.
Then to use it you have to loop over the array of rows and echo the column that you want:
foreach(getschema($mysqli) as $row) {
echo $row['naam'];
}
Or assign the function return to a variable and loop over that:
$rows = getschema($mysqli);