Flattening a SQL query result for PHP array - php

Question

I have a SQL table (modules) with two columns (id, name). Now I can retrieve the rows from this through a PHP script but what I want is to use the value of id as the key, and the value of name as the value, in a multidimensional array. Then I want to be able to encode those into a JSON, retaining the relationship between key/value. I've muddled something together but it returns null.
the relevant code from index.php
$mod1 = $core["module1"];
$mod2 = $core["module2"];
$modules = $db->getModulesById($mod1, $mod2); //module names & ids
$response["module"]["mod1"] = $modules[$mod1];
$response["module"]["mod2"] = $modules[$mod2];
$response["module"]["mod1name"] = $modules[$mod1]["name"];
$response["module"]["mod2name"] = $modules[$mod2]["name"];
echo json_encode($response);
The function from DB_Functions.php
public function getModulesById($mod1, $mod2) {
require_once 'include/Config.php';
$con = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD);
// Check connection
if (!$con)
{
die("Connection error: " . mysqli_connect_error());
}
// selecting database
mysqli_select_db($con, DB_DATABASE) or die(mysqli_connect_error());
$query = "SELECT * FROM modules WHERE id= '$mod1' OR id='$mod2'";
$result = mysqli_query($con, $query);
$arr = array();
while($row = mysqli_fetch_assoc($result)) {
// process each row
//each element of $arr now holds an id and name
$arr[] = $row;
}
// return user details
return mysqli_fetch_array($arr);
close();
}
I've looked around but I'm just not 'getting' how the query return is then broken down into key/value for a new array. If someone could ELI5 I'd appreciate it. I'm just concerned with this aspect, it's a personal project so I'm not focusing on security issues as yet, thanks.

Answer 1

You are pretty well there
public function getModulesById($mod1, $mod2) {
require_once 'include/Config.php';
$con = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_DATABASE);
// Check connection
if (!$con) {
die("Connection error: " . mysqli_connect_error());
}
$query = "SELECT * FROM modules WHERE id= '$mod1' OR id='$mod2'";
$result = mysqli_query($con, $query);
$arr = array();
while($row = mysqli_fetch_assoc($result)) {
$arr[] = $row;
}
// here is wrong
//return mysqli_fetch_array($arr);
// instead return the array youy created
return $arr;
}
And call it and then just json_encode the returned array
$mod1 = $core["module1"];
$mod2 = $core["module2"];
$modules = $db->getModulesById($mod1, $mod2); //module names & ids
$response['modules'] = $modules;
echo json_encode($response);
You should really be using prepared and paramterised queries to avoid SQL Injection like this
public function getModulesById($mod1, $mod2) {
require_once 'include/Config.php';
$con = mysqli_connect(DB_HOST, DB_USER, DB_PASSWORD, DB_DATABASE);
// Check connection
if (!$con) {
die("Connection error: " . mysqli_connect_error());
}
$sql = "SELECT * FROM modules WHERE id= ? OR id=?";
$stmt = $con->prepare($sql);
$stmt->bind_param('ii', $mod1, $mod2);
$stmt->execute();
$result = $stmt->get_result();
$arr = array();
while($row = mysqli_fetch_assoc($result)) {
$arr[] = $row;
}
// here is wrong
//return mysqli_fetch_array($arr);
// instead return the array youy created
return $arr;
}

Answer 2

mysqli_fetch_array requires the result of a mysqli_query result. Passing the constructed array to mysqli_fetch_array() is not going to work.
If you want to have a specific value from a row to use as its key, you can't resolve this with any mysqli_* function. You could however construct it yourself:
while($row = mysqli_fetch_assoc($result)) {
// process each row
//each element of $arr now holds an id and name
$arr[$row['id']] = $row;
}
mysqli_close($con);
return $arr;
You should close the connection before returning the result, code positioned after a return will not be executed.