Unset array element and reseting array values in PHP

Question

So I have 2 files. In file 1 I have a table and there I randomly select some fields and store (store in session) them in an array of 2D arrays. When I click on the cell I send this data to my file 2 where I want to check if I clicked on a randomly selected array or not and if I did, I want to remove this 2D array from an main array. But as soon as I click on one of the selected arrays, the array crashes.

File 1 PHP stuff immportant for this:

 session_start();
$_SESSION['arrays'] =  $stack ;

File 2 PHP:

session_start();

if (isset($_SESSION['arrays'])) {

    $stack = $_SESSION['arrays'];

    for ($i = 0; $i< count($stack);$i++){
        if($cooridnates == $stack[$i]){

            unset($stack[$i]);
            array_values($stack);
            $i--;
            $Result = true;
            break;
        }
    }
    $_SESSION['arrays'] =   $stack ;

I am suspecting the error might be in 2 things:

count($stack) used, but I don't believe this is the main reason.
The way I store session.

I have tried using manuals from W3Schools and official PHP website and also SOF, but with no use. But still, I am not sure if the array_values() and unset() is working correctly since the thing chrashes and I can't test it correctly.

I would appreciate any tips.

You don’t seem to have a closing } bracket for your for statement. — Dzmitry Kushnarou
– Dzmitry Kushnarou, Commented Mar 5, 2017 at 20:07

Barmar · Accepted Answer · 2017-03-05 20:11:07Z

1

You need to assign the result of array_values($stack); back to the $stack variable.

$stack = array_values($stack);

There's also no need to use $i-- when you do this, since you're breaking out of the loop after you find a match.

Instead of a loop, you can use array_search():

$pos = array_search($coordinates, $stack);
if ($pos !=== false) {
    unset $stack[$pos];
    $Result = true;
    $stack = array_values($stack);
    $_SESSION['arrays'] = $stack;
}

answered Mar 5, 2017 at 20:11

Barmar

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5 Comments

JakaStudent7 Over a year ago

You sir are a genius. I was absolutely sure I was using this in a right way. I was using official PHP site for help, but I guess I didn't use it right. I always enjoy a great tip from a more experienced member, from which I can learn a lot.

Barmar Over a year ago

@JakaStudent7 Very few functions modify arrays in place. The only common exceptions are the sorting functions and functions like array_push. In most other cases a new array is returned and you have to assign it somewhere.

JakaStudent7 Over a year ago

is the "array_splice()" function used in the same way as array_values()? Cuz I was trying to use that in the first place. but it didn't work. So I went with unset and array_values.

Barmar Over a year ago

array_splice() modifies the array -- that's the difference between it and array_slice().

JakaStudent7 Over a year ago

Oh thank you. You are a true MVP. P.S. sorry that I said Barmer in the comment of the Jain post, but I just realized that I made a spelling mistake and can't fix it anymore

Sudhanshu Jain · Accepted Answer · 2017-03-05 20:20:37Z

0

you can do this like that by using foreach loop:

session_start();
if (!empty($_SESSION['arrays'])) {
    foreach( $_SESSION['arrays'] as $key => $val){
       if($cooridnates == $val){
             unset($_SESSION['arrays'][$key]); // if you want this removed value then assign it a variable before unsetting the array
             $Result = true;
             break;
        }
    }
 }

answered Mar 5, 2017 at 20:20

Sudhanshu Jain

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4 Comments

JakaStudent7 Over a year ago

@Jain This should also work, but since I am quite new to PHP etc. I think the solution from Barmer is much easier to implement and modify in the future.

Barmar Over a year ago

This is missing the call to array_values() to renumber all the elements of the array after the element is removed.

Sudhanshu Jain Over a year ago

@jaka if you using foreach loop no matters what $index you are using it iterates on each element whether an array having a single value on array(1=>5) and if you only want to unset the field from session the you can directory unset the field then why are taking one another variable and assigning its value twice.

JakaStudent7 Over a year ago

@SudhanshuJain That is actually a great idea. I love how you exaplined this to me. Okey I will implement this and also use it in the future. Thank you. + Another thank you for the easy explenation.

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