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PHP Build a Basic PHP Website (2018) Listing and Sorting Inventory Items Adding Elements and Specifying a Key

How come changing the indexes didn't change the order of the list items?

When the foreach function was used to iterate through the array, shouldn't it start at the lowest index in the array and then go on to the next one? So when the indexes were changed how come the order of the list items stayed the same even though the last list item has the second lowest index?

Here is the code for an example:

Creating the array and setting the indexes:

<?php 
  $catalog = array();
  $catalog[101] = "Design Patterns";
  $catalog[201] = "Forest Gump";
  $catalog[301] = "Beethoven";
  $catalog[102] = "Clean Code";
?>

Then iterating through the array to add it to an unordered list:

<?php
  foreach($catalog as $item){
    echo "<li>" . $item . "</li>";
  }
?>

Shouldn't the outcome be:

<ul>
  <li>Design Patterns</li>
  <li>Clean Code</li>
  <li>Forest Gump</li>
  <li>Beethoven</li>
</ul>

But instead it comes out:

<ul>
  <li>Design Patterns</li>
  <li>Beethoven</li>
  <li>Forest Gump</li>
  <li>Clean Code</li>
</ul>

So why is this? Does foreach not start at the lowest index but instead goes through the order in which the items were added to the array? If so how does it know to do that and why doesn't it start at the lowest index?

Thanks.

1 Answer

Sean T. Unwin
Sean T. Unwin
28,660 Points

The parsing of an array is typically based upon the order which it was created, as you have seen from your example. If you want to sort an array by key then use ksort(). This would be placed after the array was created, but before the foreach function. Usage: ksort($catalog);

For further information on array sorting see the Comparison of Array Sorting Functions.

edit: Added a Snapshot to view an example; fork it to run.

I was not aware of ksort() so thank you very much for your answer and for the snapshot, cheers.