Set array value in a for loop php

Question

Apologies for the dumb question, I just can't seem to understand what's exactly going on. I have a JS function which I transformed into PHP and in the JS everything is working as desired. The problem with the PHP one is here I believe: I have last element of and array which I get by

$lastPeriod = end($periods);

while being in a for loop. Next I set the value of $lastPeriod['closeTime'] to equal a number. If I dd($lastPeriod) after changing it's value it is updated, however if I dd(); at the end it is not. Maybe there is a conflict with how I remove the next element so the end is not working correctly?

    for ( $i = 0; $i < sizeof($dailyHours); $i++ )
    {
        $periods = $dailyHours[$i]['periods'];

        for ($j = 0; $j < sizeof($periods); $j++)
        {
            $lastPeriod = end($periods);
                if ($lastPeriod['closeTime'] === '00:00'
                    && $dailyHours[$i + 1]['periods'][0]['openTime'] === '00:00'
                    && $dailyHours[$i + 1]['periods'][0]['closeTime'] !== '00:00')
                {
                    if (Carbon::parse($dailyHours[$i + 1]['periods'][0]['closeTime'])->isBefore(Carbon::createFromTimeString('11:59')))
                    {
                        $lastPeriod['closeTime'] = $dailyHours[$i + 1]['periods'][0]['closeTime'];
                        array_splice($dailyHours[$i + 1]['periods'], 0, 1);

                        if (sizeof($dailyHours[$i + 1]['periods']) < 1)
                        {
                            $dailyHours[$i + 1]['isOpen'] = 0;
                        }
                    }
                }
            }
        }
    }

Answer 1

The problem is that you are editing a copy of the array.

Let's look at this example:

<?php

$myPets = [
  [
    'animal' => 'cat',
    'name' => 'john'
  ], 
];

$pet = $myPets[0];
$pet['name'] = 'NewName';

var_dump($myPets);

When I run this program the name of my pet should be 'NewName' right?

array(1) {
  [0]=>
    array(2) {
      ["animal"]=>
        string(3) "cat"
      ["name"]=>
        string(4) "john"
    }
}

Well, as you can see the name hasn't changed. This is because when we do $pet = $myPets[0] PHP will make a copy of the $myPets[0] array.

To fix this you can take the reference of that array by doing: $pet = &$myPets[0] .

Answer 2

There are a few issues in the code:

In a loop you have this code:

$lastPeriod = end($periods);

Then later on you have:

$lastPeriod['closeTime'] = $dailyHours[$i + 1]['periods'][0]['closeTime'];

This should result in a warning

Warning: Cannot use a scalar value as an array in....

The issue that $lastPeriod = end($periods); gives you the value of the last element in the array. So if you have this array:

$dailyHours[0]['periods'][] = 23;
$dailyHours[0]['periods'][] = 12;
$dailyHours[0]['periods'][] = 5;
$dailyHours[0]['periods'][] = 8; //Last elements value in item 0

$dailyHours[1]['periods'][] = 23;
$dailyHours[1]['periods'][] = 11;
$dailyHours[1]['periods'][] = 3; //Last elements value in item 1

$dailyHours[2]['periods'][] = 5;
$dailyHours[2]['periods'][] = 12; //Last elements value in item 2

Therefore

$lastPeriod = end($periods);

would return the values 8,3 and 12.

A simplified version of your code with two loops. The outer loop ($i) and the inner loop ($j)

for ( $i = 0; $i < sizeof($dailyHours); $i++ ) {
    $periods = $dailyHours[$i]['periods']; 

    for ($j = 0; $j < sizeof($periods); $j++) {
        $lastPeriod = end($periods); //would give 8,8,8, 3,3,3 and 12,12,12

        //This would basically mean that an associative array with key closeTime
        //with the value of 8,3 or 12 => is the same as the value of $dailyHours[$i + 
        //1]['periods'][0]['closeTime'];
        //This is not a thing PHP can handle and therefore you should reviece
        //a warning "Cannot use a scalar value as an array..."
        //(You simply cannot mix numbers and associative arrays in that manner)
        $lastPeriod['closeTime'] = $dailyHours[$i + 1]['periods'][0]['closeTime'];
    }

}

Another issue is that you're trying to set a value each iteration with the same key and therefore nothing happens:

for ( $i = 0; $i < sizeof($dailyHours); $i++ ) {
    $periods = $dailyHours[$i]['periods'];

    for ($j = 0; $j < sizeof($periods); $j++) {
        $lastPeriod['closeTime'] = rand();        
        echo '<pre>';
        echo $lastPeriod['closeTime'];
        echo '</pre>';
    }

}

A possible output of the loops above code could be:

1393399136
1902598834
1291208498
654759779
493592124
1469938839
929450793
325654698
291088712

$lastPeriod['closeTime'] would be 291088712 which is the last set value above (last iteration) but the previous values set are not stored anywhere.