remove empty results with a 2nd query from array mysqli - php

Question

I have 2 tables, 1 with companies(Costcenters) and one with clients (employees of those companies)
i need to make a form to edit or delete malformed ( like john smit and j. Smit) from those companies employees grouped by company (Costcenter), when i make a list with all those companies i get a lot of companies that has no clients. So I made a array of the companies (Costcenters) and check first if they have employees, this with the goal to remove the Costcenters without employees from the array ($bedrijven).
The form is no problem, but i cant find a way to get those companies removed from the bedrijven array.
require_once('conn.php');
$query = "SELECT bedrijfID, Houder, Costcenter, Actief FROM bedrijven
WHERE Actief = 'actief' ORDER BY Costcenter";
$results = mysqli_query($conn, $query);
if (!$results) printf("Query failed: %s\n", $conn->error);
$bedrijven = [];
while($row = mysqli_fetch_assoc($results)) {
$bedrijven[] = $row['Costcenter'];
}
foreach ($bedrijven as $key => $item) {
$query1 = "SELECT * from customer where Costcenter = '$item' ORDER by
Client";
$customerresult = mysqli_query($conn, $query1) or
die(mysqli_error($conn));
if (!$customerresult) printf("Query failed: %s\n", $conn->error);
if($customerresult->num_rows === 0) {
unset($bedrijven[$key]);
}
}
I am not familiar with PDO or funtions so tried it this way that does not work as i expected, the unset is not working.
the code is editted as it is working now, i hope it might help others as well. If any has a better solution please post.

Answer 1

If I understand what you are going for, this is better done as a single Query. A JOIN can be used first to bind your tables, and then additional WHERE operators can be used if needed to refine your search. I'm not 100% sure if I'm reading right that this is is exactly how you wanted to join the data, but if you play with different JOIN operators you'll get it.
$query = "SELECT Costcenter.bedrijfID, Costcenter.Houder, Costcenter.Costcenter, Costcenter.Actief, customer.* FROM Costcenter
LEFT JOIN customer ON customer.Costcenter = Costcenter.Costcenter
WHERE Actief = 'Costcenter.actief' AND Costcenter.Costcenter != "" ORDER BY Costcenter.Costcenter";
The biggest reason for doing it this way this that a single SQL call processes WAY faster than trying to parse your data from multiple calls in PHP.

Answer 2

thanks to the requestion of The fouth bird i discovered i have been wasting a lot of time on a simple solution. i should not have done :
unset($bedrijven['Costcenter']);
but
unset($bedrijven[$key]);
you must unset the key in the array not the value....