John Davidson

Message:

I have this function to bubblesort an associative array based on a key input with the option to order by descending or ascending:

function bubbleSort($input, $key, $order){

    while (true){

        $end = false;

        $swapped = false;

        $idx = 0;

        do {

            $x = $input[$idx];

            $y = $input[$idx + 1];

            $x_param = $x[$key];

            $y_param = $y[$key];

            if (is_null($y)) {

                $end = true;

                continue;

            }

            if ($order == "desc"){

                if ($x_param < $y_param){

                    $input[$idx] = $y;

                    $input[$idx + 1] = $x;

                    $swapped = true;

                }

            }

            else{

                if ($y_param < $x_param){

                    $input[$idx] = $y;

                    $input[$idx + 1] = $x;

                    $swapped = true;

                }

            }

            $idx++;

        }

        while ($end == false);

        if ($swapped == false) {break;}

    }

    return $input;

} 

In this example I'll use it on this associative array:

$array = array(

    array("Student Number" => 001, "Student name" => "David", "Student age" => 21),

    array("Student Number" => 002, "Student name" => "Jonas", "Student age" => 15),

    array("Student Number" => 003, "Student name" => "Katy", "Student age" => 23));

If I print it with print_r like this it will successfully sort and print it:

print_r(bubbleSort($array, "Student age", "desc"));

The problem is I get Notice: Undefined offset: 3 for the line containing $y = $input[$idx + 1];

As well as Notice: Trying to access array offset on value of type null for the line containing $y_param = $y[$key];

It does print a properly sorted asc array, so the code works.

But is there a way to phrase my code to not get the notice ?

Screenshot of the full output I get (with a lot of notices).

---

My Answer:
To avoid the "Undefined offset" notice, you can modify your code to check if the next index exists before accessing it. Here's an updated version of your bubbleSort function:

php
function bubbleSort($input, $key, $order){
$length = count($input);
while (true){
$end = false;
$swapped = false;
$idx = 0;
do {
$x = $input[$idx];
$y = isset($input[$idx + 1]) ? $input[$idx + 1] : null;
if (is_null($y)) {
$end = true;
continue;
}
$x_param = $x[$key];
$y_param = $y[$key];
if ($order == "desc"){
if ($x_param < $y_param){
$input[$idx] = $y;
$input[$idx + 1] = $x;
$swapped = true;
}
}
else{
if ($y_param < $x_param){
$input[$idx] = $y;
$input[$idx + 1] = $x;
$swapped = true;
}
}
$idx++;
}
while ($end == false);
if ($swapped == false) {break;}
}
return $input;
}


By using `isset($input[$idx + 1]) ? $input[$idx + 1] : null`, you are checking if the next index exists before trying to access it. This should prevent the "Undefined offset" notice from appearing.