Yesterday I found some people on my [favorite reddit][lolphp] wonder about the output of the following code:
<?php
$a = 1;
$c = $a + $a++;
Óscar Enríquez Carmona stibiumz
nikic
/ php_evaluation_order.md
Last active
October 19, 2021 05:47
Analysis of some weird evaluation order in PHP
nikic
/ objects_arrays.md
Last active
September 24, 2024 14:51
Post explaining why objects often use less memory than arrays (in PHP)
This is just a small post in response to [this tweet][tweet] by Julien Pauli (who by the way is the release manager for PHP 5.5). In the tweet he claims that objects use more memory than arrays in PHP. Even though it can be like that, it's not true in most cases. (Note: This only applies to PHP 5.4 or newer.)
The reason why it's easy to assume that objects are larger than arrays is because objects can be seen as an array of properties and a bit of additional information (like the class it belongs to). And as array + additional info > array it obviously follows that objects are larger. The thing is that in most cases PHP can optimize the array part of it away. So how does that work?
The key here is that objects usually have a predefined set of keys, whereas arrays don't: