array_unique not removing duplicate values php - php

Question

Sorry if this is a duplicate, I have tried searching but cannot seem to find an answer. I may just have the piece of code in the wrong place.
I have counted the duplicate values input from various select boxes, which were sent over via $_GET. Using these duplicates, if more than (whatever the set amount is) then it will run through a mysql query. This is all working fine.
The issue is that I need to remove duplicates that are returned from the mysql query. Here is my code:
if ($countGearSelected >= 2) {
$gearSets = array_keys(array_filter(array_count_values($_GET['gearPiece']), function($v) {
return $v > 1;
}));
foreach ($gearSets as $gearSetKey => $gearSetValue) {
$result = mysqli_query($con,"SELECT twoPieceBonus FROM sets WHERE setName='".$gearSetValue."';");
while($row = mysqli_fetch_array($result)){
$twoPieceBonus .= urldecode($row['twoPieceBonus']).'</br></br>';
}
$twoPieceBonus = implode(',',array_unique(explode(',', $twoPieceBonus)));
$twoSelected = substr($twoPieceBonus, 0, -10);
}
}else{
$twoSelected = '';
}
As you can see, I have tried the array_unique option on various other posts on SE but it doesn't appear to be working. I think I may be using it incorrectly?
Using DISTINCT doesn't work in the mysql query, as a few of the "sets" that are being queried have the same result (if that makes sense?).
Any help is very much appreciated.

Answer 1

First: your code is vulnerable to SQL injection: use prepared statements to avoid this.
Secondly, it is often a bad idea to execute a query in each iteration of a loop. And in this case it can be avoided. Instead of an equality comparison in your where clause, you could use the in operator and compare to all gear sets in one go.
This will also solve the matter of getting distinct values. With only one query executing, you can use distinct now.
Here is how the code would look like. I could not test this, but I expect mistakes (if any) can be easily fixed:
$twoSelected = '';
if ($countGearSelected >= 2) {
$gearSets = array_keys(array_filter(
array_count_values($_GET['gearPiece']), function($v) {
return $v > 1;
}
));
// Create comma separated list of question marks
$placeHolders = implode(",", array_fill(0, count($gearSets), "?"));
// Prepare SQL statement with it
$stmt = mysqli_prepare($con,
"SELECT DISTINCT twoPieceBonus
FROM sets
WHERE setName IN ($placeHolders);");
// All gearSet values are strings:
$types = str_repeat("s", count($gearSets));
// Turn the gearSets into references
$gearSetRefs = [];
foreach ($gearSets as $i => $_) {
$gearSetRefs[] = &$gearSets[$i];
}
// Bind arguments
mysqli_stmt_bind_param($stmt, $types, ...$gearSetRefs); // the splat operator
// Now we are all set to (safely) execute the query
mysqli_stmt_execute($stmt);
$result = mysqli_stmt_get_result($stmt);
// Let the result of the URL decoding still be an array
$twoPieceBonus = [];
while ($row = mysqli_fetch_array($result)) {
$twoPieceBonus[] = urldecode($row['twoPieceBonus']);
}
mysqli_stmt_close ($stmt);
// ... and then use implode to insert those HTML breaks
$twoSelected = implode("</br></br>", $twoPieceBonus);
}